diff --git a/browser/actors/LinkHandlerChild.jsm b/browser/actors/LinkHandlerChild.jsm
index 98c3d584d72d..7b1f57055e5d 100644
--- a/browser/actors/LinkHandlerChild.jsm
+++ b/browser/actors/LinkHandlerChild.jsm
@@ -9,6 +9,8 @@ const EXPORTED_SYMBOLS = ["LinkHandlerChild"];
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/ActorChild.jsm");
 
+ChromeUtils.defineModuleGetter(this, "Feeds",
+  "resource:///modules/Feeds.jsm");
 ChromeUtils.defineModuleGetter(this, "FaviconLoader",
   "resource:///modules/FaviconLoader.jsm");
 
@@ -95,6 +97,7 @@ class LinkHandlerChild extends ActorChild {
 
     // Note: following booleans only work for the current link, not for the
     // whole content
+    let feedAdded = false;
     let iconAdded = false;
     let searchAdded = false;
     let rels = {};
@@ -105,6 +108,22 @@ class LinkHandlerChild extends ActorChild {
       let isRichIcon = false;
 
       switch (relVal) {
+        case "feed":
+        case "alternate":
+          if (!feedAdded && event.type == "DOMLinkAdded") {
+            if (!rels.feed && rels.alternate && rels.stylesheet)
+              break;
+
+            if (Feeds.isValidFeed(link, link.ownerDocument.nodePrincipal, "feed" in rels)) {
+              this.mm.sendAsyncMessage("Link:AddFeed", {
+                type: link.type,
+                href: link.href,
+                title: link.title,
+              });
+              feedAdded = true;
+            }
+          }
+          break;
         case "apple-touch-icon":
         case "apple-touch-icon-precomposed":
         case "fluid-icon":
diff --git a/browser/actors/PageInfoChild.jsm b/browser/actors/PageInfoChild.jsm
index 88cef18ae523..35cc40dbf0e9 100644
--- a/browser/actors/PageInfoChild.jsm
+++ b/browser/actors/PageInfoChild.jsm
@@ -10,6 +10,7 @@ ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/ActorChild.jsm");
 
 XPCOMUtils.defineLazyModuleGetters(this, {
+  Feeds: "resource:///modules/Feeds.jsm",
   PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.jsm",
   setTimeout: "resource://gre/modules/Timer.jsm",
 });
@@ -33,6 +34,7 @@ class PageInfoChild extends ActorChild {
 
     let pageInfoData = {metaViewRows: this.getMetaInfo(document),
                         docInfo: this.getDocumentInfo(document),
+                        feeds: this.getFeedsInfo(document, strings),
                         windowInfo: this.getWindowInfo(window)};
 
     message.target.sendAsyncMessage("PageInfo:data", pageInfoData);
@@ -96,6 +98,36 @@ class PageInfoChild extends ActorChild {
     return docInfo;
   }
 
+  getFeedsInfo(document, strings) {
+    let feeds = [];
+    // Get the feeds from the page.
+    let linkNodes = document.getElementsByTagName("link");
+    let length = linkNodes.length;
+    for (let i = 0; i < length; i++) {
+      let link = linkNodes[i];
+      if (!link.href) {
+        continue;
+      }
+      let rel = link.rel && link.rel.toLowerCase();
+      let rels = {};
+
+      if (rel) {
+        for (let relVal of rel.split(/\s+/)) {
+          rels[relVal] = true;
+        }
+      }
+
+      if (rels.feed || (link.type && rels.alternate && !rels.stylesheet)) {
+        let type = Feeds.isValidFeed(link, document.nodePrincipal, "feed" in rels);
+        if (type) {
+          type = strings[type] || strings["application/rss+xml"];
+          feeds.push([link.title, type, link.href]);
+        }
+      }
+    }
+    return feeds;
+  }
+
   // Only called once to get the media tab's media elements from the content page.
   getMediaInfo(document, window, strings, mm) {
     let frameList = this.goThroughFrames(document, window);
diff --git a/browser/base/content/browser-feeds.js b/browser/base/content/browser-feeds.js
index 5e4be6e79d1a..d5ab0b5bbeba 100644
--- a/browser/base/content/browser-feeds.js
+++ b/browser/base/content/browser-feeds.js
@@ -114,6 +114,170 @@ function getMimeTypeForFeedType(aFeedType) {
 var FeedHandler = {
   _prefChangeCallback: null,
 
+  /** Called when the user clicks on the Subscribe to This Page... menu item,
+   * or when the user clicks the feed button when the page contains multiple
+   * feeds.
+   * Builds a menu of unique feeds associated with the page, and if there
+   * is only one, shows the feed inline in the browser window.
+   * @param   container
+   *          The feed list container (menupopup or subview) to be populated.
+   * @param   isSubview
+   *          Whether we're creating a subview (true) or menu (false/undefined)
+   * @return  true if the menu/subview should be shown, false if there was only
+   *          one feed and the feed should be shown inline in the browser
+   *          window (do not show the menupopup/subview).
+   */
+  buildFeedList(container, isSubview) {
+    let feeds = gBrowser.selectedBrowser.feeds;
+    if (!isSubview && feeds == null) {
+      // XXX hack -- menu opening depends on setting of an "open"
+      // attribute, and the menu refuses to open if that attribute is
+      // set (because it thinks it's already open).  onpopupshowing gets
+      // called after the attribute is unset, and it doesn't get unset
+      // if we return false.  so we unset it here; otherwise, the menu
+      // refuses to work past this point.
+      container.parentNode.removeAttribute("open");
+      return false;
+    }
+
+    for (let i = container.childNodes.length - 1; i >= 0; --i) {
+      let node = container.childNodes[i];
+      if (isSubview && node.localName == "label")
+        continue;
+      container.removeChild(node);
+    }
+
+    if (!feeds || feeds.length <= 1)
+      return false;
+
+    // Build the menu showing the available feed choices for viewing.
+    let itemNodeType = isSubview ? "toolbarbutton" : "menuitem";
+    for (let feedInfo of feeds) {
+      let item = document.createElement(itemNodeType);
+      let baseTitle = feedInfo.title || feedInfo.href;
+      item.setAttribute("label", baseTitle);
+      item.setAttribute("feed", feedInfo.href);
+      item.setAttribute("tooltiptext", feedInfo.href);
+      item.setAttribute("crop", "center");
+      let className = "feed-" + itemNodeType;
+      if (isSubview) {
+        className += " subviewbutton";
+      }
+      item.setAttribute("class", className);
+      container.appendChild(item);
+    }
+    return true;
+  },
+
+  /**
+   * Subscribe to a given feed.  Called when
+   *   1. Page has a single feed and user clicks feed icon in location bar
+   *   2. Page has a single feed and user selects Subscribe menu item
+   *   3. Page has multiple feeds and user selects from feed icon popup (or subview)
+   *   4. Page has multiple feeds and user selects from Subscribe submenu
+   * @param   href
+   *          The feed to subscribe to. May be null, in which case the
+   *          event target's feed attribute is examined.
+   * @param   event
+   *          The event this method is handling. Used to decide where
+   *          to open the preview UI. (Optional, unless href is null)
+   */
+  subscribeToFeed(href, event) {
+    // Just load the feed in the content area to either subscribe or show the
+    // preview UI
+    if (!href)
+      href = event.target.getAttribute("feed");
+    urlSecurityCheck(href, gBrowser.contentPrincipal,
+                     Ci.nsIScriptSecurityManager.DISALLOW_INHERIT_PRINCIPAL);
+    this.loadFeed(href, event);
+  },
+
+  loadFeed(href, event) {
+    let feeds = gBrowser.selectedBrowser.feeds;
+    try {
+      openUILink(href, event, {
+        ignoreAlt: true,
+        triggeringPrincipal: gBrowser.contentPrincipal,
+      });
+    } finally {
+      // We might default to a livebookmarks modal dialog,
+      // so reset that if the user happens to click it again
+      gBrowser.selectedBrowser.feeds = feeds;
+    }
+  },
+
+  get _feedMenuitem() {
+    delete this._feedMenuitem;
+    return this._feedMenuitem = document.getElementById("subscribeToPageMenuitem");
+  },
+
+  get _feedMenupopup() {
+    delete this._feedMenupopup;
+    return this._feedMenupopup = document.getElementById("subscribeToPageMenupopup");
+  },
+
+  /**
+   * Update the browser UI to show whether or not feeds are available when
+   * a page is loaded or the user switches tabs to a page that has feeds.
+   */
+  updateFeeds() {
+    if (this._updateFeedTimeout)
+      clearTimeout(this._updateFeedTimeout);
+
+    let feeds = gBrowser.selectedBrowser.feeds;
+    let haveFeeds = feeds && feeds.length > 0;
+
+    let feedButton = document.getElementById("feed-button");
+    if (feedButton) {
+      if (haveFeeds) {
+        feedButton.removeAttribute("disabled");
+      } else {
+        feedButton.setAttribute("disabled", "true");
+      }
+    }
+
+    if (!haveFeeds) {
+      this._feedMenuitem.setAttribute("disabled", "true");
+      this._feedMenuitem.removeAttribute("hidden");
+      this._feedMenupopup.setAttribute("hidden", "true");
+      return;
+    }
+
+    if (feeds.length > 1) {
+      this._feedMenuitem.setAttribute("hidden", "true");
+      this._feedMenupopup.removeAttribute("hidden");
+    } else {
+      this._feedMenuitem.setAttribute("feed", feeds[0].href);
+      this._feedMenuitem.removeAttribute("disabled");
+      this._feedMenuitem.removeAttribute("hidden");
+      this._feedMenupopup.setAttribute("hidden", "true");
+    }
+  },
+
+  addFeed(link, browserForLink) {
+    if (!browserForLink.feeds)
+      browserForLink.feeds = [];
+
+    urlSecurityCheck(link.href, gBrowser.contentPrincipal,
+                     Ci.nsIScriptSecurityManager.DISALLOW_INHERIT_PRINCIPAL);
+
+    let feedURI = makeURI(link.href, document.characterSet);
+    if (!/^https?$/.test(feedURI.scheme))
+      return;
+
+    browserForLink.feeds.push({ href: link.href, title: link.title });
+
+    // If this addition was for the current browser, update the UI. For
+    // background browsers, we'll update on tab switch.
+    if (browserForLink == gBrowser.selectedBrowser) {
+      // Batch updates to avoid updating the UI for multiple onLinkAdded events
+      // fired within 100ms of each other.
+      if (this._updateFeedTimeout)
+        clearTimeout(this._updateFeedTimeout);
+      this._updateFeedTimeout = setTimeout(this.updateFeeds.bind(this), 100);
+    }
+  },
+
    /**
    * Get the human-readable display name of a file. This could be the
    * application name.
diff --git a/browser/base/content/browser-menubar.inc b/browser/base/content/browser-menubar.inc
index 1a5054f37a39..0b95444aaa3b 100644
--- a/browser/base/content/browser-menubar.inc
+++ b/browser/base/content/browser-menubar.inc
@@ -400,6 +400,26 @@
       <menuitem id="menu_bookmarkThisPage"
                 command="Browser:AddBookmarkAs"
                 key="addBookmarkAsKb"/>
+      <menuitem id="subscribeToPageMenuitem"
+                disabled="true"
+#ifndef XP_MACOSX
+                class="menuitem-iconic"
+#endif
+                label="&subscribeToPageMenuitem.label;"
+                oncommand="return FeedHandler.subscribeToFeed(null, event);"
+                onclick="checkForMiddleClick(this, event);"
+                />
+      <menu id="subscribeToPageMenupopup"
+            hidden="true"
+#ifndef XP_MACOSX
+            class="menu-iconic"
+#endif
+            label="&subscribeToPageMenupopup.label;">
+        <menupopup id="subscribeToPageSubmenuMenupopup"
+                   onpopupshowing="return FeedHandler.buildFeedList(event.target);"
+                   oncommand="return FeedHandler.subscribeToFeed(null, event);"
+                   onclick="checkForMiddleClick(this, event);"/>
+      </menu>
       <menuitem id="menu_bookmarkAllTabs"
                 label="&addCurPagesCmd.label;"
                 class="show-only-for-keyboard"
diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 72bb01986bd4..a49b2f6aca18 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -3661,6 +3661,7 @@ var newWindowButtonObserver = {
 const DOMEventHandler = {
   init() {
     let mm = window.messageManager;
+    mm.addMessageListener("Link:AddFeed", this);
     mm.addMessageListener("Link:LoadingIcon", this);
     mm.addMessageListener("Link:SetIcon", this);
     mm.addMessageListener("Link:SetFailedIcon", this);
@@ -3670,6 +3671,11 @@ const DOMEventHandler = {
 
   receiveMessage(aMsg) {
     switch (aMsg.name) {
+      case "Link:AddFeed":
+        let link = {type: aMsg.data.type, href: aMsg.data.href, title: aMsg.data.title};
+        FeedHandler.addFeed(link, aMsg.target);
+        break;
+
       case "Link:LoadingIcon":
         if (aMsg.data.canUseForTab) {
           this.setPendingIcon(aMsg.target);
@@ -4702,6 +4708,9 @@ var XULBrowserWindow = {
         aStateFlags & nsIWebProgressListener.STATE_IS_NETWORK) {
 
       if (aRequest && aWebProgress.isTopLevel) {
+        // clear out feed data
+        browser.feeds = null;
+
         // clear out search-engine data
         browser.engines = null;
       }
@@ -4931,6 +4940,7 @@ var XULBrowserWindow = {
   },
 
   asyncUpdateUI() {
+    FeedHandler.updateFeeds();
     BrowserSearch.updateOpenSearchBadge();
   },
 
diff --git a/browser/base/content/pageinfo/feeds.js b/browser/base/content/pageinfo/feeds.js
new file mode 100644
index 000000000000..612eec6f8cc2
--- /dev/null
+++ b/browser/base/content/pageinfo/feeds.js
@@ -0,0 +1,60 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Via pageInfo.xul -> utilityOverlay.js
+/* import-globals-from ../utilityOverlay.js */
+/* import-globals-from ./pageInfo.js */
+
+function initFeedTab(feeds) {
+  for (const [name, type, url] of feeds) {
+    addRow(name, type, url);
+  }
+
+  const feedListbox = document.getElementById("feedListbox");
+  document.getElementById("feedTab").hidden = feedListbox.getRowCount() == 0;
+}
+
+function addRow(name, type, url) {
+  const item = document.createXULElement("richlistitem");
+
+  const top = document.createXULElement("hbox");
+  top.setAttribute("flex", "1");
+  item.appendChild(top);
+
+  const bottom = document.createXULElement("hbox");
+  bottom.setAttribute("flex", "1");
+  item.appendChild(bottom);
+
+  const nameLabel = document.createXULElement("label");
+  nameLabel.className = "feedTitle";
+  nameLabel.textContent = name;
+  nameLabel.setAttribute("flex", "1");
+  top.appendChild(nameLabel);
+
+  const typeLabel = document.createXULElement("label");
+  typeLabel.textContent = type;
+  top.appendChild(typeLabel);
+
+  const urlContainer = document.createXULElement("hbox");
+  urlContainer.setAttribute("flex", "1");
+  bottom.appendChild(urlContainer);
+
+  const urlLabel = document.createXULElement("label");
+  urlLabel.className = "text-link";
+  urlLabel.textContent = url;
+  urlLabel.setAttribute("tooltiptext", url);
+  urlLabel.addEventListener("click", ev => openUILink(this.value, ev, {triggeringPrincipal: Services.scriptSecurityManager.createNullPrincipal({})}));
+  urlContainer.appendChild(urlLabel);
+
+  const subscribeButton = document.createXULElement("button");
+  subscribeButton.className = "feed-subscribe";
+  subscribeButton.addEventListener("click",
+    () => openWebLinkIn(url, "current", { ignoreAlt: true }));
+  subscribeButton.setAttribute("label", gBundle.getString("feedSubscribe"));
+  subscribeButton.setAttribute("accesskey", gBundle.getString("feedSubscribe.accesskey"));
+  bottom.appendChild(subscribeButton);
+
+  document.getElementById("feedListbox").appendChild(item);
+}
diff --git a/browser/base/content/pageinfo/pageInfo.css b/browser/base/content/pageinfo/pageInfo.css
index 26c7729da370..e8adeef192b7 100644
--- a/browser/base/content/pageinfo/pageInfo.css
+++ b/browser/base/content/pageinfo/pageInfo.css
@@ -12,6 +12,14 @@
   display: none;
 }
 
+#feedListbox richlistitem {
+  -moz-box-orient: vertical;
+}
+
+#feedListbox richlistitem:not([selected="true"]) .feed-subscribe {
+  display: none;
+}
+
 groupbox[closed="true"] > .groupbox-body {
   visibility: collapse;
 }
diff --git a/browser/base/content/pageinfo/pageInfo.js b/browser/base/content/pageinfo/pageInfo.js
index b78e6390a59f..c37d237caa76 100644
--- a/browser/base/content/pageinfo/pageInfo.js
+++ b/browser/base/content/pageinfo/pageInfo.js
@@ -7,7 +7,7 @@ ChromeUtils.import("resource://gre/modules/Services.jsm");
 /* import-globals-from ../../../../toolkit/content/globalOverlay.js */
 /* import-globals-from ../../../../toolkit/content/contentAreaUtils.js */
 /* import-globals-from ../../../../toolkit/content/treeUtils.js */
-/* import-globals-from ../utilityOverlay.js */
+/* import-globals-from feeds.js */
 /* import-globals-from permissions.js */
 /* import-globals-from security.js */
 
@@ -333,6 +333,12 @@ function loadPageInfo(frameOuterWindowID, imageElement, browser) {
   browser = browser || window.opener.gBrowser.selectedBrowser;
   let mm = browser.messageManager;
 
+  gStrings["application/rss+xml"]  = gBundle.getString("feedRss");
+  gStrings["application/atom+xml"] = gBundle.getString("feedAtom");
+  gStrings["text/xml"]             = gBundle.getString("feedXML");
+  gStrings["application/xml"]      = gBundle.getString("feedXML");
+  gStrings["application/rdf+xml"]  = gBundle.getString("feedXML");
+
   let imageInfo = imageElement;
 
   // Look for pageInfoListener in content.js. Sends message to listener with arguments.
@@ -340,7 +346,7 @@ function loadPageInfo(frameOuterWindowID, imageElement, browser) {
 
   let pageInfoData;
 
-  // Get initial pageInfoData needed to display the general, permission and security tabs.
+  // Get initial pageInfoData needed to display the general, feeds, permission and security tabs.
   mm.addMessageListener("PageInfo:data", function onmessage(message) {
     mm.removeMessageListener("PageInfo:data", onmessage);
     pageInfoData = message.data;
@@ -359,6 +365,7 @@ function loadPageInfo(frameOuterWindowID, imageElement, browser) {
     document.getElementById("main-window").setAttribute("relatedUrl", docInfo.location);
 
     makeGeneralTab(pageInfoData.metaViewRows, docInfo);
+    initFeedTab(pageInfoData.feeds);
     onLoadPermission(uri, principal);
     securityOnLoad(uri, windowInfo);
   });
@@ -402,6 +409,11 @@ function resetPageInfo(args) {
   gImageView.clear();
   gImageHash = {};
 
+  /* Reset Feeds Tab */
+  var feedListbox = document.getElementById("feedListbox");
+  while (feedListbox.firstChild)
+    feedListbox.firstChild.remove();
+
   /* Call registered overlay reset functions */
   onResetRegistry.forEach(function(func) { func(); });
 
@@ -423,6 +435,7 @@ function doHelpButton() {
   const helpTopics = {
     "generalPanel":  "pageinfo_general",
     "mediaPanel":    "pageinfo_media",
+    "feedPanel":     "pageinfo_feed",
     "permPanel":     "pageinfo_permissions",
     "securityPanel": "pageinfo_security",
   };
diff --git a/browser/base/content/pageinfo/pageInfo.xul b/browser/base/content/pageinfo/pageInfo.xul
index 5c6269162e01..2c7b872355ce 100644
--- a/browser/base/content/pageinfo/pageInfo.xul
+++ b/browser/base/content/pageinfo/pageInfo.xul
@@ -32,6 +32,7 @@
   <script type="application/javascript" src="chrome://global/content/contentAreaUtils.js"/>
   <script type="application/javascript" src="chrome://global/content/treeUtils.js"/>
   <script type="application/javascript" src="chrome://browser/content/pageinfo/pageInfo.js"/>
+  <script type="application/javascript" src="chrome://browser/content/pageinfo/feeds.js"/>
   <script type="application/javascript" src="chrome://browser/content/pageinfo/permissions.js"/>
   <script type="application/javascript" src="chrome://browser/content/pageinfo/security.js"/>
   <script type="application/javascript" src="chrome://browser/content/utilityOverlay.js"/>
@@ -73,6 +74,8 @@
            oncommand="showTab('general');"/>
       <radio id="mediaTab"    label="&mediaTab;"    accesskey="&mediaTab.accesskey;"
            oncommand="showTab('media');" hidden="true"/>
+      <radio id="feedTab"     label="&feedTab;"     accesskey="&feedTab.accesskey;"
+           oncommand="showTab('feed');" hidden="true"/>
       <radio id="permTab"     label="&permTab;"     accesskey="&permTab.accesskey;"
            oncommand="showTab('perm');"/>
       <radio id="securityTab" label="&securityTab;" accesskey="&securityTab.accesskey;"
@@ -261,6 +264,11 @@
       </hbox>
     </vbox>
 
+    <!-- Feeds -->
+    <vbox id="feedPanel">
+      <richlistbox id="feedListbox" flex="1"/>
+    </vbox>
+
     <!-- Permissions -->
     <vbox id="permPanel">
       <hbox id="permHostBox">
diff --git a/browser/base/content/test/general/browser.ini b/browser/base/content/test/general/browser.ini
index 0c3fd736b0f5..92e47e2b842b 100644
--- a/browser/base/content/test/general/browser.ini
+++ b/browser/base/content/test/general/browser.ini
@@ -33,6 +33,7 @@ support-files =
   download_page_1.txt
   download_page_2.txt
   dummy_page.html
+  feed_tab.html
   file_documentnavigation_frameset.html
   file_double_close_tab.html
   file_fullscreen-window-open.html
@@ -95,6 +96,8 @@ skip-if = (verify && !debug && (os == 'win'))
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_bug406216.js]
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
+[browser_bug413915.js]
+# DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_bug416661.js]
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_bug417483.js]
@@ -335,6 +338,9 @@ subsuite = clipboard
 support-files = offlineQuotaNotification.cacheManifest offlineQuotaNotification.html
 skip-if = os == "linux" && !debug # bug 1304273
 # DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
+[browser_feed_discovery.js]
+support-files = feed_discovery.html
+# DO NOT ADD MORE TESTS HERE. USE A TOPICAL DIRECTORY INSTEAD.
 [browser_gZipOfflineChild.js]
 skip-if = verify
 support-files = test_offline_gzip.html gZipOfflineChild.cacheManifest gZipOfflineChild.cacheManifest^headers^ gZipOfflineChild.html gZipOfflineChild.html^headers^
diff --git a/browser/base/content/test/general/browser_bug413915.js b/browser/base/content/test/general/browser_bug413915.js
new file mode 100644
index 000000000000..3abe9fc365ff
--- /dev/null
+++ b/browser/base/content/test/general/browser_bug413915.js
@@ -0,0 +1,68 @@
+ChromeUtils.defineModuleGetter(this, "Feeds",
+  "resource:///modules/Feeds.jsm");
+
+function test() {
+  var exampleUri = makeURI("http://example.com/");
+  var principal = Services.scriptSecurityManager.createCodebasePrincipal(exampleUri, {});
+
+  function testIsFeed(aTitle, aHref, aType, aKnown) {
+    var link = {
+      title: aTitle,
+      href: aHref,
+      type: aType,
+      ownerDocument: {
+        characterSet: "UTF-8",
+      },
+    };
+    return Feeds.isValidFeed(link, principal, aKnown);
+  }
+
+  var href = "http://example.com/feed/";
+  var atomType = "application/atom+xml";
+  var funkyAtomType = " aPPLICAtion/Atom+XML ";
+  var rssType = "application/rss+xml";
+  var funkyRssType = " Application/RSS+XML  ";
+  var rdfType = "application/rdf+xml";
+  var texmlType = "text/xml";
+  var appxmlType = "application/xml";
+  var noRss = "Foo";
+  var rss = "RSS";
+
+  // things that should be valid
+  ok(testIsFeed(noRss, href, atomType, false) == atomType,
+     "detect Atom feed");
+  ok(testIsFeed(noRss, href, funkyAtomType, false) == atomType,
+     "clean up and detect Atom feed");
+  ok(testIsFeed(noRss, href, rssType, false) == rssType,
+     "detect RSS feed");
+  ok(testIsFeed(noRss, href, funkyRssType, false) == rssType,
+     "clean up and detect RSS feed");
+
+  // things that should not be feeds
+  ok(testIsFeed(noRss, href, rdfType, false) == null,
+     "should not detect RDF non-feed");
+  ok(testIsFeed(rss, href, rdfType, false) == null,
+     "should not detect RDF feed from type and title");
+  ok(testIsFeed(noRss, href, texmlType, false) == null,
+     "should not detect text/xml non-feed");
+  ok(testIsFeed(rss, href, texmlType, false) == null,
+     "should not detect text/xml feed from type and title");
+  ok(testIsFeed(noRss, href, appxmlType, false) == null,
+     "should not detect application/xml non-feed");
+  ok(testIsFeed(rss, href, appxmlType, false) == null,
+     "should not detect application/xml feed from type and title");
+
+  // security check only, returns cleaned up type or "application/rss+xml"
+  ok(testIsFeed(noRss, href, atomType, true) == atomType,
+     "feed security check should return Atom type");
+  ok(testIsFeed(noRss, href, funkyAtomType, true) == atomType,
+     "feed security check should return cleaned up Atom type");
+  ok(testIsFeed(noRss, href, rssType, true) == rssType,
+     "feed security check should return RSS type");
+  ok(testIsFeed(noRss, href, funkyRssType, true) == rssType,
+     "feed security check should return cleaned up RSS type");
+  ok(testIsFeed(noRss, href, "", true) == rssType,
+     "feed security check without type should return RSS type");
+  ok(testIsFeed(noRss, href, "garbage", true) == "garbage",
+     "feed security check with garbage type should return garbage");
+}
diff --git a/browser/base/content/test/general/browser_feed_discovery.js b/browser/base/content/test/general/browser_feed_discovery.js
new file mode 100644
index 000000000000..c698cf1cb2a8
--- /dev/null
+++ b/browser/base/content/test/general/browser_feed_discovery.js
@@ -0,0 +1,33 @@
+const URL = "http://mochi.test:8888/browser/browser/base/content/test/general/feed_discovery.html";
+
+/** Test for Bug 377611 **/
+
+add_task(async function() {
+  // Open a new tab.
+  gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser, URL);
+  registerCleanupFunction(() => gBrowser.removeCurrentTab());
+
+  let browser = gBrowser.selectedBrowser;
+  await BrowserTestUtils.browserLoaded(browser);
+
+  let discovered = browser.feeds;
+  ok(discovered.length > 0, "some feeds should be discovered");
+
+  let feeds = {};
+  for (let aFeed of discovered) {
+    feeds[aFeed.href] = true;
+  }
+
+  await ContentTask.spawn(browser, feeds, async function(contentFeeds) {
+    for (let aLink of content.document.getElementsByTagName("link")) {
+      // ignore real stylesheets, and anything without an href property
+      if (aLink.type != "text/css" && aLink.href) {
+        if (/bogus/i.test(aLink.title)) {
+          ok(!contentFeeds[aLink.href], "don't discover " + aLink.href);
+        } else {
+          ok(contentFeeds[aLink.href], "should discover " + aLink.href);
+        }
+      }
+    }
+  });
+});
diff --git a/browser/base/content/test/general/feed_discovery.html b/browser/base/content/test/general/feed_discovery.html
new file mode 100644
index 000000000000..7682b281835c
--- /dev/null
+++ b/browser/base/content/test/general/feed_discovery.html
@@ -0,0 +1,78 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=377611
+-->
+  <head>
+    <title>Test for feed discovery</title>
+    <meta charset="utf-8">
+
+    <!-- Straight up standard -->
+    <link rel="alternate" type="application/atom+xml" title="1" href="/1.atom" />
+    <link rel="alternate" type="application/rss+xml" title="2" href="/2.rss" />
+    <link rel="feed" title="3" href="/3.xml" />
+
+    <!-- invalid protocol -->
+    <link rel="alternate" type="application/atom+xml" title="Bogus non file protocol" href="file://path/1.rss" />
+    <link rel="alternate" type="application/atom+xml" title="Bogus non feed:http protocol" href="feed:http://path/1.rss" />
+    <link rel="alternate" type="application/atom+xml" title="Bogus non pcast protocol" href="pcast://path/1.rss" />
+
+    <!-- rel is a space-separated list -->
+    <link rel=" alternate " type="application/atom+xml" title="4" href="/4.atom" />
+    <link rel="foo alternate" type="application/atom+xml" title="5" href="/5.atom" />
+    <link rel="alternate foo" type="application/atom+xml" title="6" href="/6.atom" />
+    <link rel="foo alternate foo" type="application/atom+xml" title="7" href="/7.atom" />
+    <link rel="meat feed cake" title="8" href="/8.atom" />
+
+    <!-- rel is case-insensitive -->
+    <link rel="ALTERNate" type="application/atom+xml" title="9" href="/9.atom" />
+    <link rel="fEEd" title="10" href="/10.atom" />
+
+    <!-- type can have leading and trailing whitespace -->
+    <link rel="alternate" type="  application/atom+xml  " title="11" href="/11.atom" />
+
+    <!-- type is case-insensitive -->
+    <link rel="alternate" type="aPPliCAtion/ATom+xML" title="12" href="/12.atom" />
+
+    <!-- "feed stylesheet" is a feed, though "alternate stylesheet" isn't -->
+    <link rel="feed stylesheet" title="13" href="/13.atom" />
+
+    <!-- hyphens or letters around rel not allowed -->
+    <link rel="disabled-alternate" type="application/atom+xml" title="Bogus1" href="/Bogus1" />
+    <link rel="alternates" type="application/atom+xml" title="Bogus2" href="/Bogus2" />
+    <link rel=" alternate-like" type="application/atom+xml" title="Bogus3" href="/Bogus3" />
+
+    <!-- don't tolerate text/xml if title includes 'rss' not as a word -->
+    <link rel="alternate" type="text/xml" title="Bogus4 scissorsshaped" href="/Bogus4" />
+
+    <!-- don't tolerate application/xml if title includes 'rss' not as a word -->
+    <link rel="alternate" type="application/xml" title="Bogus5 scissorsshaped" href="/Bogus5" />
+
+    <!-- don't tolerate application/rdf+xml if title includes 'rss' not as a word -->
+    <link rel="alternate" type="application/rdf+xml" title="Bogus6 scissorsshaped" href="/Bogus6" />
+
+    <!-- don't tolerate random types -->
+    <link rel="alternate" type="text/plain" title="Bogus7 rss" href="/Bogus7" />
+
+    <!-- don't find Atom by title -->
+    <link rel="foopy" type="application/atom+xml" title="Bogus8 Atom and RSS" href="/Bogus8" />
+
+    <!-- don't find application/rss+xml by title -->
+    <link rel="goats" type="application/rss+xml" title="Bogus9 RSS and Atom" href="/Bogus9" />
+
+    <!-- don't find application/rdf+xml by title -->
+    <link rel="alternate" type="application/rdf+xml" title="Bogus10 RSS and Atom" href="/Bogus10" />
+
+    <!-- don't find application/xml by title -->
+    <link rel="alternate" type="application/xml" title="Bogus11 RSS and Atom" href="/Bogus11" />
+
+    <!-- don't find text/xml by title -->
+    <link rel="alternate" type="text/xml" title="Bogus12 RSS and Atom" href="/Bogus12" />
+
+    <!-- alternate and stylesheet isn't a feed -->
+    <link rel="alternate stylesheet" type="application/rss+xml" title="Bogus13 RSS" href="/Bogus13" />
+  </head>
+  <body>
+  </body>
+</html>
+
diff --git a/browser/base/content/test/pageinfo/browser.ini b/browser/base/content/test/pageinfo/browser.ini
index 32621e99bd55..9b9e75fab8ea 100644
--- a/browser/base/content/test/pageinfo/browser.ini
+++ b/browser/base/content/test/pageinfo/browser.ini
@@ -1,5 +1,8 @@
 [DEFAULT]
 
+[browser_pageInfo.js]
+support-files =
+  ../general/feed_tab.html
 [browser_pageinfo_firstPartyIsolation.js]
 support-files =
   image.html
diff --git a/browser/base/content/test/pageinfo/browser_pageInfo.js b/browser/base/content/test/pageinfo/browser_pageInfo.js
new file mode 100644
index 000000000000..8d51c405fd3a
--- /dev/null
+++ b/browser/base/content/test/pageinfo/browser_pageInfo.js
@@ -0,0 +1,39 @@
+const URI = "https://example.com/browser/browser/base/content/test/pageinfo/feed_tab.html";
+
+function test() {
+  waitForExplicitFinish();
+
+  var pageInfo;
+
+  gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser, false,
+                                 URI).then(() => {
+    Services.obs.addObserver(observer, "page-info-dialog-loaded");
+    pageInfo = BrowserPageInfo();
+  });
+  gBrowser.selectedBrowser.loadURI(URI);
+
+  function observer(win, topic, data) {
+    Services.obs.removeObserver(observer, "page-info-dialog-loaded");
+    pageInfo.onFinished.push(handlePageInfo);
+  }
+
+  function handlePageInfo() {
+    ok(pageInfo.document.getElementById("feedTab"), "Feed tab");
+    let feedListbox = pageInfo.document.getElementById("feedListbox");
+    ok(feedListbox, "Feed list should exist.");
+
+    var feedRowsNum = feedListbox.getRowCount();
+    is(feedRowsNum, 3, "Number of feeds listed should be correct.");
+
+    for (var i = 0; i < feedRowsNum; i++) {
+      let feedItem = feedListbox.getItemAtIndex(i);
+      let feedTitle = feedItem.querySelector(".feedTitle");
+      is(feedTitle.textContent, i + 1, "Feed name should be correct.");
+    }
+
+    pageInfo.close();
+    gBrowser.removeCurrentTab();
+    finish();
+  }
+}
diff --git a/browser/base/content/theme-vars.inc.css b/browser/base/content/theme-vars.inc.css
index 0b6f390a169f..b0ed3e92150a 100644
--- a/browser/base/content/theme-vars.inc.css
+++ b/browser/base/content/theme-vars.inc.css
@@ -105,6 +105,10 @@
   list-style-image: var(--sidebars-icon) !important;
 }
 
+:root[lwthemeicons~="--subscribe-icon"] #feed-button:-moz-lwtheme {
+  list-style-image: var(--subscribe-icon) !important;
+}
+
 :root[lwthemeicons~="--text_encoding-icon"] #characterencoding-button:-moz-lwtheme {
   list-style-image: var(--text_encoding-icon) !important;
 }
@@ -143,6 +147,7 @@
 :root[lwthemeicons~="--synced_tabs-icon"] #sync-button:-moz-lwtheme,
 :root[lwthemeicons~="--open_file-icon"] #open-file-button:-moz-lwtheme,
 :root[lwthemeicons~="--sidebars-icon"] #sidebar-button:-moz-lwtheme,
+:root[lwthemeicons~="--subscribe-icon"] #feed-button:-moz-lwtheme,
 :root[lwthemeicons~="--text_encoding-icon"] #characterencoding-button:-moz-lwtheme,
 :root[lwthemeicons~="--email_link-icon"] #email-link-button:-moz-lwtheme,
 :root[lwthemeicons~="--forget-icon"] #panic-button:-moz-lwtheme {
diff --git a/browser/base/jar.mn b/browser/base/jar.mn
index 1da3d8c7232d..b80b3fa637bf 100644
--- a/browser/base/jar.mn
+++ b/browser/base/jar.mn
@@ -82,6 +82,7 @@ browser.jar:
 *       content/browser/pageinfo/pageInfo.xul         (content/pageinfo/pageInfo.xul)
         content/browser/pageinfo/pageInfo.js          (content/pageinfo/pageInfo.js)
         content/browser/pageinfo/pageInfo.css         (content/pageinfo/pageInfo.css)
+        content/browser/pageinfo/feeds.js             (content/pageinfo/feeds.js)
         content/browser/pageinfo/permissions.js       (content/pageinfo/permissions.js)
         content/browser/pageinfo/security.js          (content/pageinfo/security.js)
         content/browser/content-refreshblocker.js     (content/content-refreshblocker.js)
diff --git a/browser/components/customizableui/CustomizableUI.jsm b/browser/components/customizableui/CustomizableUI.jsm
index 2159731391df..fd82e5d8bfb1 100644
--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -55,7 +55,7 @@ const kSubviewEvents = [
  * The current version. We can use this to auto-add new default widgets as necessary.
  * (would be const but isn't because of testing purposes)
  */
-var kVersion = 15;
+var kVersion = 14;
 
 /**
  * Buttons removed from built-ins by version they were removed. kVersion must be
@@ -63,7 +63,6 @@ var kVersion = 15;
  * version the button is removed in as the value.  e.g. "pocket-button": 5
  */
 var ObsoleteBuiltinButtons = {
-  "feed-button": 15,
 };
 
 /**
diff --git a/browser/components/customizableui/CustomizableWidgets.jsm b/browser/components/customizableui/CustomizableWidgets.jsm
index 2fd9dd9ef88b..37bb2de29ae4 100644
--- a/browser/components/customizableui/CustomizableWidgets.jsm
+++ b/browser/components/customizableui/CustomizableWidgets.jsm
@@ -329,6 +329,44 @@ const CustomizableWidgets = [
     },
   },
   {
+    id: "feed-button",
+    type: "view",
+    viewId: "PanelUI-feeds",
+    tooltiptext: "feed-button.tooltiptext2",
+    onClick(aEvent) {
+      let win = aEvent.target.ownerGlobal;
+      let feeds = win.gBrowser.selectedBrowser.feeds;
+
+      // Here, we only care about the case where we have exactly 1 feed and the
+      // user clicked...
+      let isClick = (aEvent.button == 0 || aEvent.button == 1);
+      if (feeds && feeds.length == 1 && isClick) {
+        aEvent.preventDefault();
+        aEvent.stopPropagation();
+        win.FeedHandler.subscribeToFeed(feeds[0].href, aEvent);
+        CustomizableUI.hidePanelForNode(aEvent.target);
+      }
+    },
+    onViewShowing(aEvent) {
+      let doc = aEvent.target.ownerDocument;
+      let container = doc.getElementById("PanelUI-feeds");
+      let gotView = doc.defaultView.FeedHandler.buildFeedList(container, true);
+
+      // For no feeds or only a single one, don't show the panel.
+      if (!gotView) {
+        aEvent.preventDefault();
+        aEvent.stopPropagation();
+      }
+    },
+    onCreated(node) {
+      let win = node.ownerGlobal;
+      let selectedBrowser = win.gBrowser.selectedBrowser;
+      let feeds = selectedBrowser && selectedBrowser.feeds;
+      if (!feeds || !feeds.length) {
+        node.setAttribute("disabled", "true");
+      }
+    },
+  }, {
     id: "characterencoding-button",
     label: "characterencoding-button2.label",
     type: "view",
diff --git a/browser/components/customizableui/test/browser.ini b/browser/components/customizableui/test/browser.ini
index 77f589bfac4f..3ce405ba5820 100644
--- a/browser/components/customizableui/test/browser.ini
+++ b/browser/components/customizableui/test/browser.ini
@@ -2,6 +2,8 @@
 support-files =
   head.js
   support/test_967000_charEncoding_page.html
+  support/feeds_test_page.html
+  support/test-feed.xml
 
 [browser_694291_searchbar_preference.js]
 [browser_873501_handle_specials.js]
@@ -93,6 +95,8 @@ skip-if = verify
 skip-if = verify
 [browser_963639_customizing_attribute_non_customizable_toolbar.js]
 [browser_967000_button_charEncoding.js]
+[browser_967000_button_feeds.js]
+skip-if = (verify && debug && (os == 'linux'))
 [browser_968565_insert_before_hidden_items.js]
 [browser_969427_recreate_destroyed_widget_after_reset.js]
 [browser_969661_character_encoding_navbar_disabled.js]
diff --git a/browser/components/customizableui/test/browser_1042100_default_placements_update.js b/browser/components/customizableui/test/browser_1042100_default_placements_update.js
index e01e25b56cb2..3e69ab7b3aaa 100644
--- a/browser/components/customizableui/test/browser_1042100_default_placements_update.js
+++ b/browser/components/customizableui/test/browser_1042100_default_placements_update.js
@@ -7,7 +7,7 @@
 // don't try this at home, kids.
 function test() {
   // Customize something to make sure stuff changed:
-  CustomizableUI.addWidgetToArea("save-page-button", CustomizableUI.AREA_NAVBAR);
+  CustomizableUI.addWidgetToArea("feed-button", CustomizableUI.AREA_NAVBAR);
 
   // Check what version we're on:
   let CustomizableUIBSPass = ChromeUtils.import("resource:///modules/CustomizableUI.jsm", {});
diff --git a/browser/components/customizableui/test/browser_1161838_inserted_new_default_buttons.js b/browser/components/customizableui/test/browser_1161838_inserted_new_default_buttons.js
index 585d1822fabe..2808a092a44f 100644
--- a/browser/components/customizableui/test/browser_1161838_inserted_new_default_buttons.js
+++ b/browser/components/customizableui/test/browser_1161838_inserted_new_default_buttons.js
@@ -4,7 +4,7 @@
 // don't try this at home, kids.
 function test() {
   // Customize something to make sure stuff changed:
-  CustomizableUI.addWidgetToArea("save-page-button", CustomizableUI.AREA_NAVBAR);
+  CustomizableUI.addWidgetToArea("feed-button", CustomizableUI.AREA_NAVBAR);
 
   let CustomizableUIBSPass = ChromeUtils.import("resource:///modules/CustomizableUI.jsm", {});
 
diff --git a/browser/components/customizableui/test/browser_876926_customize_mode_wrapping.js b/browser/components/customizableui/test/browser_876926_customize_mode_wrapping.js
index 9dd18bfad30f..0c73ece05661 100644
--- a/browser/components/customizableui/test/browser_876926_customize_mode_wrapping.js
+++ b/browser/components/customizableui/test/browser_876926_customize_mode_wrapping.js
@@ -5,7 +5,7 @@
 "use strict";
 
 const kXULWidgetId = "a-test-button"; // we'll create a button with this ID.
-const kAPIWidgetId = "save-page-button";
+const kAPIWidgetId = "feed-button";
 const kPanel = CustomizableUI.AREA_FIXED_OVERFLOW_PANEL;
 const kToolbar = CustomizableUI.AREA_NAVBAR;
 const kVisiblePalette = "customization-palette";
diff --git a/browser/components/customizableui/test/browser_878452_drag_to_panel.js b/browser/components/customizableui/test/browser_878452_drag_to_panel.js
index 3163ebd8dd68..dfc08f559b6c 100644
--- a/browser/components/customizableui/test/browser_878452_drag_to_panel.js
+++ b/browser/components/customizableui/test/browser_878452_drag_to_panel.js
@@ -8,12 +8,12 @@ CustomizableUI.createWidget({id: "cui-panel-item-to-drag-to", defaultArea: Custo
 // Dragging an item from the palette to another button in the panel should work.
 add_task(async function() {
   await startCustomizing();
-  let btn = document.getElementById("new-window-button");
+  let btn = document.getElementById("feed-button");
   let placements = getAreaWidgetIds(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
 
   let lastButtonIndex = placements.length - 1;
   let lastButton = placements[lastButtonIndex];
-  let placementsAfterInsert = placements.slice(0, lastButtonIndex).concat(["new-window-button", lastButton]);
+  let placementsAfterInsert = placements.slice(0, lastButtonIndex).concat(["feed-button", lastButton]);
   let lastButtonNode = document.getElementById(lastButton);
   simulateItemDrag(btn, lastButtonNode, "start");
   assertAreaPlacements(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL, placementsAfterInsert);
@@ -28,11 +28,11 @@ add_task(async function() {
 add_task(async function() {
   CustomizableUI.addWidgetToArea("cui-panel-item-to-drag-to", CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
   await startCustomizing();
-  let btn = document.getElementById("new-window-button");
+  let btn = document.getElementById("feed-button");
   let panel = document.getElementById(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
   let placements = getAreaWidgetIds(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
 
-  let placementsAfterAppend = placements.concat(["new-window-button"]);
+  let placementsAfterAppend = placements.concat(["feed-button"]);
   simulateItemDrag(btn, panel);
   assertAreaPlacements(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL, placementsAfterAppend);
   ok(!CustomizableUI.inDefaultState, "Should no longer be in default state.");
@@ -49,12 +49,12 @@ add_task(async function() {
     CustomizableUI.removeWidgetFromArea(widgetIds.shift());
   }
   await startCustomizing();
-  let btn = document.getElementById("new-window-button");
+  let btn = document.getElementById("feed-button");
   let panel = document.getElementById(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
 
   assertAreaPlacements(panel.id, []);
 
-  let placementsAfterAppend = ["new-window-button"];
+  let placementsAfterAppend = ["feed-button"];
   simulateItemDrag(btn, panel);
   assertAreaPlacements(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL, placementsAfterAppend);
   ok(!CustomizableUI.inDefaultState, "Should no longer be in default state.");
diff --git a/browser/components/customizableui/test/browser_887438_currentset_shim.js b/browser/components/customizableui/test/browser_887438_currentset_shim.js
index ae581493e684..0e306ea83bdf 100644
--- a/browser/components/customizableui/test/browser_887438_currentset_shim.js
+++ b/browser/components/customizableui/test/browser_887438_currentset_shim.js
@@ -29,10 +29,10 @@ add_task(function() {
 // Insert, then remove items
 add_task(function() {
   let currentSet = navbar.currentSet;
-  let newCurrentSet = currentSet.replace("home-button", "new-window-button,sync-button,home-button");
+  let newCurrentSet = currentSet.replace("home-button", "feed-button,sync-button,home-button");
   navbar.currentSet = newCurrentSet;
   is(newCurrentSet, navbar.currentSet, "Current set should match expected current set.");
-  let feedBtn = document.getElementById("new-window-button");
+  let feedBtn = document.getElementById("feed-button");
   let syncBtn = document.getElementById("sync-button");
   ok(feedBtn, "Feed button should have been added.");
   ok(syncBtn, "Sync button should have been added.");
@@ -54,10 +54,10 @@ add_task(function() {
 // Simultaneous insert/remove:
 add_task(function() {
   let currentSet = navbar.currentSet;
-  let newCurrentSet = currentSet.replace("home-button", "new-window-button");
+  let newCurrentSet = currentSet.replace("home-button", "feed-button");
   navbar.currentSet = newCurrentSet;
   is(newCurrentSet, navbar.currentSet, "Current set should match expected current set.");
-  let feedBtn = document.getElementById("new-window-button");
+  let feedBtn = document.getElementById("feed-button");
   ok(feedBtn, "Feed button should have been added.");
   let homeBtn = document.getElementById("home-button");
   ok(!homeBtn, "Home button should have been removed.");
diff --git a/browser/components/customizableui/test/browser_967000_button_feeds.js b/browser/components/customizableui/test/browser_967000_button_feeds.js
new file mode 100644
index 000000000000..9a75f2db3660
--- /dev/null
+++ b/browser/components/customizableui/test/browser_967000_button_feeds.js
@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const TEST_PAGE = "http://mochi.test:8888/browser/browser/components/customizableui/test/support/feeds_test_page.html";
+const TEST_FEED = "http://mochi.test:8888/browser/browser/components/customizableui/test/support/test-feed.xml";
+
+var newTab = null;
+var initialLocation = gBrowser.currentURI.spec;
+
+add_task(async function() {
+  info("Check Subscribe button functionality");
+
+  // add the Subscribe button to the panel
+  CustomizableUI.addWidgetToArea("feed-button",
+                                  CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
+
+  await waitForOverflowButtonShown();
+
+  // check the button's functionality
+  await document.getElementById("nav-bar").overflowable.show();
+
+  let feedButton = document.getElementById("feed-button");
+  ok(feedButton, "The Subscribe button was added to the Panel Menu");
+  is(feedButton.getAttribute("disabled"), "true", "The Subscribe button is initially disabled");
+
+  let panelHidePromise = promiseOverflowHidden(window);
+  await document.getElementById("nav-bar").overflowable._panel.hidePopup();
+  await panelHidePromise;
+
+  newTab = gBrowser.selectedTab;
+  await promiseTabLoadEvent(newTab, TEST_PAGE);
+
+  await gCUITestUtils.openMainMenu();
+
+  await waitForCondition(() => !feedButton.hasAttribute("disabled"));
+  ok(!feedButton.hasAttribute("disabled"), "The Subscribe button gets enabled");
+
+  feedButton.click();
+  await promiseTabLoadEvent(newTab, TEST_FEED);
+
+  is(gBrowser.currentURI.spec, TEST_FEED, "Subscribe page opened");
+  ok(!isOverflowOpen(), "Panel is closed");
+
+  if (isOverflowOpen()) {
+    panelHidePromise = promiseOverflowHidden(window);
+    await document.getElementById("nav-bar").overflowable._panel.hidePopup();
+    await panelHidePromise;
+  }
+});
+
+add_task(async function asyncCleanup() {
+  // reset the panel UI to the default state
+  await resetCustomization();
+  ok(CustomizableUI.inDefaultState, "The UI is in default state again.");
+
+  // restore the initial location
+  BrowserTestUtils.addTab(gBrowser, initialLocation);
+  gBrowser.removeTab(newTab);
+});
diff --git a/browser/components/customizableui/test/browser_996364_registerArea_different_properties.js b/browser/components/customizableui/test/browser_996364_registerArea_different_properties.js
index 89b55b545393..b9de5f687b72 100644
--- a/browser/components/customizableui/test/browser_996364_registerArea_different_properties.js
+++ b/browser/components/customizableui/test/browser_996364_registerArea_different_properties.js
@@ -79,7 +79,7 @@ add_task(function() {
                                                    defaultPlacements: [] });
     CustomizableUI.registerArea("area-996899-2", { anchor: "PanelUI-menu-button",
                                                    type: CustomizableUI.TYPE_MENU_PANEL,
-                                                   defaultPlacements: ["new-window-button"] });
+                                                   defaultPlacements: ["feed-button"] });
   } catch (ex) {
     exceptionThrown = ex;
   }
diff --git a/browser/components/customizableui/test/support/feeds_test_page.html b/browser/components/customizableui/test/support/feeds_test_page.html
new file mode 100644
index 000000000000..be78e4dff6a0
--- /dev/null
+++ b/browser/components/customizableui/test/support/feeds_test_page.html
@@ -0,0 +1,10 @@
+<html>
+<head>
+  <title>Feeds test page</title>
+  <link rel="alternate" type="application/rss+xml" href="test-feed.xml" title="Test feed">
+</head>
+
+<body>
+  This is a test page for feeds
+</body>
+</html>
diff --git a/browser/components/customizableui/test/support/test-feed.xml b/browser/components/customizableui/test/support/test-feed.xml
new file mode 100644
index 000000000000..0e700b6d8dd3
--- /dev/null
+++ b/browser/components/customizableui/test/support/test-feed.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title>
+  <link href="http://example.org/"/>
+  <updated>2010-08-22T18:30:02Z</updated>
+
+  <author>
+    <name>John Doe</name>
+  </author>
+  <id>urn:uuid:e2df8375-99be-4848-b05e-b9d407555267</id>
+
+  <entry>
+
+    <title>Item</title>
+    <link href="http://example.org/first"/>
+    <id>urn:uuid:9e0f4bed-33d3-4a9d-97ab-ecaa31b3f14a</id>
+    <updated>2010-08-22T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/extensions/test/browser/browser_ext_themes_icons.js b/browser/components/extensions/test/browser/browser_ext_themes_icons.js
index 6f6e1a3b72e7..59480080230e 100644
--- a/browser/components/extensions/test/browser/browser_ext_themes_icons.js
+++ b/browser/components/extensions/test/browser/browser_ext_themes_icons.js
@@ -120,6 +120,7 @@ async function runTestWithIcons(icons) {
     ["synced_tabs", "#sync-button", "sync-button"],
     ["open_file", "#open-file-button", "open-file-button"],
     ["sidebars", "#sidebar-button", "sidebar-button"],
+    ["subscribe", "#feed-button", "feed-button"],
     ["text_encoding", "#characterencoding-button", "characterencoding-button"],
     ["email_link", "#email-link-button", "email-link-button"],
     ["forget", "#panic-button", "panic-button"],
@@ -192,6 +193,7 @@ add_task(async function test_all_icons() {
     ["synced_tabs", "fox.svg"],
     ["open_file", "fox.svg"],
     ["sidebars", "fox.svg"],
+    ["subscribe", "fox.svg"],
     ["text_encoding", "fox.svg"],
     ["email_link", "fox.svg"],
     ["forget", "fox.svg"],
@@ -231,6 +233,7 @@ add_task(async function test_some_icons() {
     ["synced_tabs", ""],
     ["open_file", ""],
     ["sidebars", ""],
+    ["subscribe", ""],
     ["text_encoding", ""],
     ["email_link", ""],
     ["forget", ""],
diff --git a/browser/components/feeds/FeedConverter.js b/browser/components/feeds/FeedConverter.js
index 02f2db8634c0..dadf20682890 100644
--- a/browser/components/feeds/FeedConverter.js
+++ b/browser/components/feeds/FeedConverter.js
@@ -341,6 +341,12 @@ FeedResultService.prototype = {
                                        subtitle,
                                        feedHandler: "default" });
       break;
+    default:
+      // fall through
+    case "bookmarks":
+      Services.cpmm.sendAsyncMessage("FeedConverter:addLiveBookmark",
+                                     { spec, title });
+      break;
     }
   },
 
diff --git a/browser/components/feeds/FeedWriter.js b/browser/components/feeds/FeedWriter.js
index 5b4db1b5eee0..4d44de14a2a3 100644
--- a/browser/components/feeds/FeedWriter.js
+++ b/browser/components/feeds/FeedWriter.js
@@ -68,7 +68,15 @@ XPCOMUtils.defineLazyPreferenceGetter(this, "gCanFrameFeeds",
   "browser.feeds.unsafelyFrameFeeds", false);
 
 function FeedWriter() {
+  this._selectedApp = undefined;
+  this._selectedAppMenuItem = null;
+  this._subscribeCallback = null;
+  this._defaultHandlerMenuItem = null;
+
   Services.telemetry.scalarAdd("browser.feeds.preview_loaded", 1);
+
+  XPCOMUtils.defineLazyGetter(this, "_mm",
+                              () => this._window.docShell.messageManager);
 }
 
 FeedWriter.prototype = {
@@ -138,6 +146,24 @@ FeedWriter.prototype = {
     return this._bundle.GetStringFromName(key);
   },
 
+  _setCheckboxCheckedState(aValue) {
+    let checkbox = this._document.getElementById("alwaysUse");
+    if (checkbox) {
+      // see checkbox.xml, xbl bindings are not applied within the sandbox! TODO
+      let change = (aValue != (checkbox.getAttribute("checked") == "true"));
+      if (aValue)
+        checkbox.setAttribute("checked", "true");
+      else
+        checkbox.removeAttribute("checked");
+
+      if (change) {
+        let event = this._document.createEvent("Events");
+        event.initEvent("CheckboxStateChange", true, true);
+        checkbox.dispatchEvent(event);
+      }
+    }
+  },
+
    /**
    * Returns a date suitable for displaying in the feed preview.
    * If the date cannot be parsed, the return value is "false".
@@ -167,6 +193,25 @@ FeedWriter.prototype = {
     return this.__dateFormatter;
   },
 
+  /**
+   * Returns the feed type.
+   */
+  __feedType: null,
+  _getFeedType() {
+    if (this.__feedType != null)
+      return this.__feedType;
+
+    try {
+      // grab the feed because it's got the feed.type in it.
+      let container = this._getContainer();
+      let feed = container.QueryInterface(Ci.nsIFeed);
+      this.__feedType = feed.type;
+      return feed.type;
+    } catch (ex) { }
+
+    return Ci.nsIFeed.TYPE_FEED;
+  },
+
   /**
    * Writes the feed title into the preview document.
    * @param   container
@@ -427,6 +472,234 @@ FeedWriter.prototype = {
     return container;
   },
 
+  /**
+   * Get moz-icon url for a file
+   * @param   file
+   *          A nsIFile object for which the moz-icon:// is returned
+   * @returns moz-icon url of the given file as a string
+   */
+  _getFileIconURL(file) {
+    let fph = Services.io.getProtocolHandler("file")
+                 .QueryInterface(Ci.nsIFileProtocolHandler);
+    let urlSpec = fph.getURLSpecFromFile(file);
+    return "moz-icon://" + urlSpec + "?size=16";
+  },
+
+  /**
+   * Displays a prompt from which the user may choose a (client) feed reader.
+   * @param aCallback the callback method, passes in true if a feed reader was
+   *        selected, false otherwise.
+   */
+  _chooseClientApp(aCallback) {
+    this._subscribeCallback = aCallback;
+    this._mm.sendAsyncMessage("FeedWriter:ChooseClientApp",
+                              { title: this._getString("chooseApplicationDialogTitle"),
+                                feedType: this._getFeedType() });
+  },
+
+  _setSubscribeUsingLabel() {
+    let stringLabel = "subscribeFeedUsing";
+    switch (this._getFeedType()) {
+      case Ci.nsIFeed.TYPE_VIDEO:
+        stringLabel = "subscribeVideoPodcastUsing";
+        break;
+
+      case Ci.nsIFeed.TYPE_AUDIO:
+        stringLabel = "subscribeAudioPodcastUsing";
+        break;
+    }
+
+    let subscribeUsing = this._document.getElementById("subscribeUsingDescription");
+    let textNode = this._document.createTextNode(this._getString(stringLabel));
+    subscribeUsing.insertBefore(textNode, subscribeUsing.firstChild);
+  },
+
+  _setAlwaysUseLabel() {
+    let checkbox = this._document.getElementById("alwaysUse");
+    if (checkbox && this._handlersList) {
+      let handlerName = this._handlersList.selectedOptions[0]
+                            .textContent;
+      let stringLabel = "alwaysUseForFeeds";
+      switch (this._getFeedType()) {
+        case Ci.nsIFeed.TYPE_VIDEO:
+          stringLabel = "alwaysUseForVideoPodcasts";
+          break;
+
+        case Ci.nsIFeed.TYPE_AUDIO:
+          stringLabel = "alwaysUseForAudioPodcasts";
+          break;
+      }
+
+      let label = this._getFormattedString(stringLabel, [handlerName]);
+
+      let checkboxText = this._document.getElementById("checkboxText");
+      if (checkboxText.lastChild.nodeType == checkboxText.TEXT_NODE) {
+        checkboxText.lastChild.textContent = label;
+      } else {
+        LOG("FeedWriter._setAlwaysUseLabel: Expected textNode as lastChild of alwaysUse label");
+        let textNode = this._document.createTextNode(label);
+        checkboxText.appendChild(textNode);
+      }
+    }
+  },
+
+  // EventListener
+  handleEvent(event) {
+    if (event.target.ownerDocument != this._document) {
+      LOG("FeedWriter.handleEvent: Someone passed the feed writer as a listener to the events of another document!");
+      return;
+    }
+
+    switch (event.type) {
+      case "click":
+        if (event.target.id == "subscribeButton") {
+          this.subscribe();
+        }
+      break;
+      case "change":
+        LOG("Change fired");
+        if (event.target.selectedOptions[0].id == "chooseApplicationMenuItem") {
+          this._chooseClientApp(() => {
+            // Select the (per-prefs) selected handler if no application
+            // was selected
+            LOG("Selected handler after callback");
+            this._setAlwaysUseLabel();
+          });
+        } else {
+          this._setAlwaysUseLabel();
+        }
+        break;
+    }
+  },
+
+  _setSelectedHandlerResponse(handler) {
+    LOG(`Selecting handler response ${handler}`);
+    switch (handler) {
+      case "client":
+      case "default":
+        // do nothing, these are handled by the onchange event
+        break;
+      case "bookmarks":
+      default: {
+        let liveBookmarksMenuItem = this._document.getElementById("liveBookmarksMenuItem");
+        if (liveBookmarksMenuItem)
+          liveBookmarksMenuItem.selected = true;
+      }
+    }
+  },
+
+  _initSubscriptionUI(setupMessage) {
+    if (!this._handlersList)
+      return;
+    LOG("UI init");
+
+    let feedType = this._getFeedType();
+
+    // change the background
+    let header = this._document.getElementById("feedHeader");
+    switch (feedType) {
+      case Ci.nsIFeed.TYPE_VIDEO:
+        header.className = "videoPodcastBackground";
+        break;
+
+      case Ci.nsIFeed.TYPE_AUDIO:
+        header.className = "audioPodcastBackground";
+        break;
+
+      default:
+        header.className = "feedBackground";
+    }
+
+    let liveBookmarksMenuItem = this._document.getElementById("liveBookmarksMenuItem");
+
+    // Last-selected application
+    let menuItem = liveBookmarksMenuItem.cloneNode(false);
+    menuItem.removeAttribute("selected");
+    menuItem.setAttribute("id", "selectedAppMenuItem");
+    menuItem.setAttribute("handlerType", "client");
+
+    // Hide the menuitem until we select an app
+    menuItem.style.display = "none";
+    this._selectedAppMenuItem = menuItem;
+
+    this._handlersList.appendChild(this._selectedAppMenuItem);
+
+    // Create the menuitem for the default reader, but don't show/populate it until
+    // we get confirmation of what it is from the parent
+    menuItem = liveBookmarksMenuItem.cloneNode(false);
+    menuItem.removeAttribute("selected");
+    menuItem.setAttribute("id", "defaultHandlerMenuItem");
+    menuItem.setAttribute("handlerType", "client");
+    menuItem.style.display = "none";
+
+    this._defaultHandlerMenuItem = menuItem;
+    this._handlersList.appendChild(this._defaultHandlerMenuItem);
+
+    // "Choose Application..." menuitem
+    menuItem = liveBookmarksMenuItem.cloneNode(false);
+    menuItem.removeAttribute("selected");
+    menuItem.setAttribute("id", "chooseApplicationMenuItem");
+    menuItem.textContent = this._getString("chooseApplicationMenuItem");
+
+    this._handlersList.appendChild(menuItem);
+
+    this._setSelectedHandlerResponse(setupMessage.reader.handler);
+
+    if (setupMessage.defaultMenuItem) {
+      LOG(`Setting default menu item ${setupMessage.defaultMenuItem}`);
+      this._setApplicationLauncherMenuItem(this._defaultHandlerMenuItem, setupMessage.defaultMenuItem);
+    }
+    if (setupMessage.selectedMenuItem) {
+      LOG(`Setting selected menu item ${setupMessage.selectedMenuItem}`);
+      this._setApplicationLauncherMenuItem(this._selectedAppMenuItem, setupMessage.selectedMenuItem);
+    }
+
+    // "Subscribe using..."
+    this._setSubscribeUsingLabel();
+
+    // "Always use..." checkbox initial state
+    this._setCheckboxCheckedState(setupMessage.reader.alwaysUse);
+    this._setAlwaysUseLabel();
+
+    // We update the "Always use.." checkbox label whenever the selected item
+    // in the list is changed
+    this._handlersList.addEventListener("change", this);
+
+    // Set up the "Subscribe Now" button
+    this._document.getElementById("subscribeButton")
+        .addEventListener("click", this);
+
+    // first-run ui
+    if (setupMessage.showFirstRunUI) {
+      let textfeedinfo1, textfeedinfo2;
+      switch (feedType) {
+        case Ci.nsIFeed.TYPE_VIDEO:
+          textfeedinfo1 = "feedSubscriptionVideoPodcast1";
+          textfeedinfo2 = "feedSubscriptionVideoPodcast2";
+          break;
+        case Ci.nsIFeed.TYPE_AUDIO:
+          textfeedinfo1 = "feedSubscriptionAudioPodcast1";
+          textfeedinfo2 = "feedSubscriptionAudioPodcast2";
+          break;
+        default:
+          textfeedinfo1 = "feedSubscriptionFeed1";
+          textfeedinfo2 = "feedSubscriptionFeed2";
+      }
+
+      let feedinfo1 = this._document.getElementById("feedSubscriptionInfo1");
+      let feedinfo1Str = this._getString(textfeedinfo1);
+      let feedinfo2 = this._document.getElementById("feedSubscriptionInfo2");
+      let feedinfo2Str = this._getString(textfeedinfo2);
+
+      feedinfo1.textContent = feedinfo1Str;
+      feedinfo2.textContent = feedinfo2Str;
+
+      header.setAttribute("firstrun", "true");
+
+      this._mm.sendAsyncMessage("FeedWriter:ShownFirstRun");
+    }
+  },
+
   /**
    * Returns the original URI object of the feed and ensures that this
    * component is only ever invoked from the preview document.
@@ -462,6 +735,7 @@ FeedWriter.prototype = {
   _document: null,
   _feedURI: null,
   _feedPrincipal: null,
+  _handlersList: null,
 
   // BrowserFeedWriter WebIDL methods
   init(aWindow) {
@@ -475,10 +749,73 @@ FeedWriter.prototype = {
 
     this._window = window;
     this._document = window.document;
+    this._handlersList = this._document.getElementById("handlersMenuList");
 
     this._feedPrincipal = Services.scriptSecurityManager.createCodebasePrincipal(this._feedURI, {});
 
     LOG("Subscribe Preview: feed uri = " + this._window.location.href);
+
+
+    this._mm.addMessageListener("FeedWriter:PreferenceUpdated", this);
+    this._mm.addMessageListener("FeedWriter:SetApplicationLauncherMenuItem", this);
+    this._mm.addMessageListener("FeedWriter:GetSubscriptionUIResponse", this);
+
+    const feedType = this._getFeedType();
+    this._mm.sendAsyncMessage("FeedWriter:GetSubscriptionUI",
+                              { feedType });
+  },
+
+  receiveMessage(msg) {
+    if (!this._window) {
+      // this._window is null unless this.init was called with a trusted
+      // window object.
+      return;
+    }
+    LOG(`received message from parent ${msg.name}`);
+    switch (msg.name) {
+      case "FeedWriter:PreferenceUpdated":
+        // This is called when browser-feeds.js spots a pref change
+        // This will happen when
+        // - about:preferences#general changes
+        // - another feed reader page changes the preference
+        // - when this page itself changes the select and there isn't a redirect
+        //   bookmarks and launching an external app means the page stays open after subscribe
+        const feedType = this._getFeedType();
+        LOG(`Got prefChange! ${JSON.stringify(msg.data)} current type: ${feedType}`);
+        let feedTypePref = msg.data.default;
+        if (feedType in msg.data) {
+          feedTypePref = msg.data[feedType];
+        }
+        LOG(`Got pref ${JSON.stringify(feedTypePref)}`);
+        this._setCheckboxCheckedState(feedTypePref.alwaysUse);
+        this._setSelectedHandlerResponse(feedTypePref.handler);
+        this._setAlwaysUseLabel();
+        break;
+      case "FeedWriter:GetSubscriptionUIResponse":
+        // Set up the subscription UI
+        this._initSubscriptionUI(msg.data);
+        break;
+      case "FeedWriter:SetApplicationLauncherMenuItem":
+        LOG(`FeedWriter:SetApplicationLauncherMenuItem - picked ${msg.data.name}`);
+        this._setApplicationLauncherMenuItem(this._selectedAppMenuItem, msg.data.name);
+        // Potentially a bit racy, but I don't think we can get into a state where this callback is set and
+        // we're not coming back from ChooseClientApp in browser-feeds.js
+        if (this._subscribeCallback) {
+          this._subscribeCallback();
+          this._subscribeCallback = null;
+        }
+        break;
+    }
+  },
+
+  _setApplicationLauncherMenuItem(menuItem, aName) {
+    /* unselect all handlers */
+    [...this._handlersList.children].forEach((option) => {
+      option.removeAttribute("selected");
+    });
+    menuItem.textContent = aName;
+    menuItem.style.display = "";
+    menuItem.selected = true;
   },
 
   writeContent() {
@@ -503,12 +840,21 @@ FeedWriter.prototype = {
     if (!this._window) {
       return;
     }
+    this._document.getElementById("subscribeButton")
+        .removeEventListener("click", this);
+    this._handlersList
+        .removeEventListener("change", this);
     this._document = null;
     this._window = null;
+    this._handlersList = null;
 
     this._removeFeedFromCache();
     this.__bundle = null;
     this._feedURI = null;
+
+    this._selectedApp = undefined;
+    this._selectedAppMenuItem = null;
+    this._defaultHandlerMenuItem = null;
   },
 
   _removeFeedFromCache() {
@@ -520,6 +866,69 @@ FeedWriter.prototype = {
     }
   },
 
+  subscribe() {
+    if (!this._window) {
+      return;
+    }
+    let feedType = this._getFeedType();
+
+    // Subscribe to the feed using the selected handler and save prefs
+    let defaultHandler = "reader";
+    let useAsDefault = this._document.getElementById("alwaysUse").getAttribute("checked");
+
+    let selectedItem = this._handlersList.selectedOptions[0];
+    let subscribeCallback = () => {
+      let feedReader = null;
+      let settings = {
+        feedType,
+        useAsDefault,
+        // Pull the title and subtitle out of the document
+        feedTitle: this._document.getElementById(TITLE_ID).textContent,
+        feedSubtitle: this._document.getElementById(SUBTITLE_ID).textContent,
+        feedLocation: this._window.location.href,
+      };
+      switch (selectedItem.id) {
+        case "selectedAppMenuItem":
+          feedReader = "client";
+          break;
+        case "defaultHandlerMenuItem":
+          feedReader = "default";
+          break;
+        case "liveBookmarksMenuItem":
+          defaultHandler = "bookmarks";
+          feedReader = "bookmarks";
+          break;
+      }
+      settings.reader = feedReader;
+
+      // If "Always use..." is checked, we should set PREF_*SELECTED_ACTION
+      // to either "reader" (If an application is selected),
+      // or to "bookmarks" (if the live bookmarks option is selected).
+      // Otherwise, we should set it to "ask"
+      if (!useAsDefault) {
+        defaultHandler = "ask";
+      }
+      settings.action = defaultHandler;
+      LOG(`FeedWriter:SetFeedPrefsAndSubscribe - ${JSON.stringify(settings)}`);
+      this._mm.sendAsyncMessage("FeedWriter:SetFeedPrefsAndSubscribe",
+                                settings);
+    };
+
+    // Show the file picker before subscribing if the
+    // choose application menuitem was chosen using the keyboard
+    if (selectedItem.id == "chooseApplicationMenuItem") {
+      this._chooseClientApp(aResult => {
+        if (aResult) {
+          selectedItem =
+            this._handlersList.selectedOptions[0];
+          subscribeCallback();
+        }
+      });
+    } else {
+      subscribeCallback();
+    }
+  },
+
   classID: FEEDWRITER_CID,
   QueryInterface: ChromeUtils.generateQI([Ci.nsIObserver,
                                           Ci.nsIDOMGlobalPropertyInitializer]),
diff --git a/browser/components/feeds/content/subscribe.xhtml b/browser/components/feeds/content/subscribe.xhtml
index c8465c6274f3..d780c9ac527f 100644
--- a/browser/components/feeds/content/subscribe.xhtml
+++ b/browser/components/feeds/content/subscribe.xhtml
@@ -36,6 +36,18 @@
           <p id="feedSubscriptionInfo1" />
           <p id="feedSubscriptionInfo2" />
         </div>
+        <div id="feedSubscribeLine">
+          <label id="subscribeUsingDescription">
+            <select id="handlersMenuList">
+              <option id="liveBookmarksMenuItem" selected="true">&feedLiveBookmarks;</option>
+              <option disabled="true">&#x2501;&#x2501;&#x2501;&#x2501;&#x2501;&#x2501;&#x2501;</option>
+            </select>
+          </label>
+          <label id="checkboxText">
+            <input type="checkbox" id="alwaysUse" class="alwaysUse" checked="false"/>
+          </label>
+          <button id="subscribeButton">&feedSubscribeNow;</button>
+        </div>
       </div>
       <div id="feedHeaderContainerSpacer"/>
     </div>
diff --git a/browser/components/feeds/test/browser/browser.ini b/browser/components/feeds/test/browser/browser.ini
index 8f9c9a715c6d..e6ba96cd5d1e 100644
--- a/browser/components/feeds/test/browser/browser.ini
+++ b/browser/components/feeds/test/browser/browser.ini
@@ -1,3 +1,6 @@
 [browser_registerProtocolHandler_notification.js]
 support-files =
   browser_registerProtocolHandler_notification.html
+[browser_telemetry_checks.js]
+support-files =
+  valid-feed.xml
diff --git a/browser/components/feeds/test/browser/browser_telemetry_checks.js b/browser/components/feeds/test/browser/browser_telemetry_checks.js
new file mode 100644
index 000000000000..640bb4fa8921
--- /dev/null
+++ b/browser/components/feeds/test/browser/browser_telemetry_checks.js
@@ -0,0 +1,96 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function() {
+  function getSnapShot() {
+    return Services.telemetry.snapshotScalars(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTOUT, false);
+  }
+  const TEST_PATH = getRootDirectory(gTestPath).replace("chrome://mochitests/content", "http://example.com");
+  const FEED_URI = TEST_PATH + "valid-feed.xml";
+
+  // Ensure we don't have any pre-existing telemetry that'd mess up counts in here:
+  Services.telemetry.clearScalars();
+  const kScalarPrefix = "browser.feeds.";
+  const kPreviewLoaded = kScalarPrefix + "preview_loaded";
+  const kSubscribed = kScalarPrefix + "feed_subscribed";
+  const kLivemarkCount = kScalarPrefix + "livebookmark_count";
+  const kLivemarkOpened = kScalarPrefix + "livebookmark_opened";
+  const kLivemarkItemOpened = kScalarPrefix + "livebookmark_item_opened";
+
+  let scalarForContent = gMultiProcessBrowser ? "content" : "parent";
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, FEED_URI);
+  // Ensure we get telemetry from the content process:
+  let previewCount = await TestUtils.waitForCondition(() => {
+    let snapshot = getSnapShot()[scalarForContent];
+    return snapshot && snapshot[kPreviewLoaded];
+  });
+  Assert.equal(previewCount, 1, "Should register the preview in telemetry.");
+
+  // Now check subscription. We stub out the actual code for adding the live bookmark,
+  // because the dialog creates an initial copy of the bookmark when it's opened and
+  // that's hard to deal with deterministically in tests.
+  let old = PlacesCommandHook.addLiveBookmark;
+  let createBMPromise = new Promise(resolve => {
+    PlacesCommandHook.addLiveBookmark = function(...args) {
+      resolve(args);
+      // Return the promise because Feeds.jsm expects a promise:
+      return createBMPromise;
+    };
+  });
+  registerCleanupFunction(() => PlacesCommandHook.addLiveBookmark = old);
+  await BrowserTestUtils.synthesizeMouseAtCenter("#subscribeButton", {}, tab.linkedBrowser);
+  let bmArgs = await createBMPromise;
+  Assert.deepEqual(bmArgs, [FEED_URI, "Example Feed"], "Should have been trying to subscribe");
+  let snapshot = getSnapShot();
+  Assert.equal(snapshot.parent[kSubscribed], 1, "Should have subscribed once.");
+
+  // Now manually add a livemark in the menu and one in the bookmarks toolbar:
+  let livemarks = await Promise.all([
+    PlacesUtils.livemarks.addLivemark({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      feedURI: Services.io.newURI(FEED_URI),
+    }),
+    PlacesUtils.livemarks.addLivemark({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      feedURI: Services.io.newURI(FEED_URI),
+    }),
+  ]);
+  registerCleanupFunction(async () => {
+    for (let mark of livemarks) {
+      await PlacesUtils.livemarks.removeLivemark(mark);
+    }
+  });
+
+  if (document.getElementById("PersonalToolbar").getAttribute("collapsed") == "true") {
+    CustomizableUI.setToolbarVisibility("PersonalToolbar", true);
+    registerCleanupFunction(() => CustomizableUI.setToolbarVisibility("PersonalToolbar", false));
+  }
+
+  // Force updating telemetry:
+  let {PlacesDBUtils} = ChromeUtils.import("resource://gre/modules/PlacesDBUtils.jsm", {});
+  await PlacesDBUtils._telemetryForFeeds();
+  Assert.equal(getSnapShot().parent[kLivemarkCount], 2,
+    "Should have created two livemarks and counted them.");
+
+  info("Waiting for livemark");
+  // Check we count opening the livemark popup:
+  let livemarkOnToolbar = await TestUtils.waitForCondition(
+    () => document.querySelector("#PersonalToolbar .bookmark-item[livemark]"));
+  let popup = livemarkOnToolbar.querySelector("menupopup");
+  let popupShownPromise = BrowserTestUtils.waitForEvent(popup, "popupshown");
+  info("Clicking on livemark");
+  // Using .click() or .doCommand() doesn't seem to work.
+  EventUtils.synthesizeMouseAtCenter(livemarkOnToolbar, {});
+  await popupShownPromise;
+  Assert.equal(getSnapShot().parent[kLivemarkOpened], 1, "Should count livemark opening");
+
+  // And opening an item in the popup:
+  let item = await TestUtils.waitForCondition(
+    () => popup.querySelector("menuitem.bookmark-item"));
+  item.doCommand();
+  Assert.equal(getSnapShot().parent[kLivemarkItemOpened], 1, "Should count livemark item opening");
+  popup.hidePopup();
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/browser/components/feeds/test/browser/valid-feed.xml b/browser/components/feeds/test/browser/valid-feed.xml
new file mode 100644
index 000000000000..0e700b6d8dd3
--- /dev/null
+++ b/browser/components/feeds/test/browser/valid-feed.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title>
+  <link href="http://example.org/"/>
+  <updated>2010-08-22T18:30:02Z</updated>
+
+  <author>
+    <name>John Doe</name>
+  </author>
+  <id>urn:uuid:e2df8375-99be-4848-b05e-b9d407555267</id>
+
+  <entry>
+
+    <title>Item</title>
+    <link href="http://example.org/first"/>
+    <id>urn:uuid:9e0f4bed-33d3-4a9d-97ab-ecaa31b3f14a</id>
+    <updated>2010-08-22T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/feeds/test/bug589543-data.xml b/browser/components/feeds/test/bug589543-data.xml
new file mode 100644
index 000000000000..0e700b6d8dd3
--- /dev/null
+++ b/browser/components/feeds/test/bug589543-data.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title>
+  <link href="http://example.org/"/>
+  <updated>2010-08-22T18:30:02Z</updated>
+
+  <author>
+    <name>John Doe</name>
+  </author>
+  <id>urn:uuid:e2df8375-99be-4848-b05e-b9d407555267</id>
+
+  <entry>
+
+    <title>Item</title>
+    <link href="http://example.org/first"/>
+    <id>urn:uuid:9e0f4bed-33d3-4a9d-97ab-ecaa31b3f14a</id>
+    <updated>2010-08-22T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/feeds/test/mochitest.ini b/browser/components/feeds/test/mochitest.ini
index f0747fa05a57..a742b2c1b3e0 100644
--- a/browser/components/feeds/test/mochitest.ini
+++ b/browser/components/feeds/test/mochitest.ini
@@ -7,6 +7,7 @@ support-files =
   bug408328-data.xml
   bug436801-data.xml
   bug494328-data.xml
+  bug589543-data.xml
   valid-feed.xml
   valid-unsniffable-feed.xml
 
@@ -16,5 +17,6 @@ support-files =
   bug364677-data.xml^headers^
 [test_bug436801.html]
 [test_bug494328.html]
+[test_bug589543.html]
 [test_registerHandler.html]
 [test_registerHandler_disabled.html]
diff --git a/browser/components/feeds/test/test_bug589543.html b/browser/components/feeds/test/test_bug589543.html
new file mode 100644
index 000000000000..cee2a9661039
--- /dev/null
+++ b/browser/components/feeds/test/test_bug589543.html
@@ -0,0 +1,32 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=589543
+-->
+<head>
+  <title>Test feed preview subscribe UI</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=589543">Mozilla Bug 589543</a>
+<p id="display"><iframe id="testFrame" src="bug589543-data.xml"></iframe></p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 589543 **/
+SimpleTest.waitForExplicitFinish();
+
+addLoadEvent(function() {
+  var doc = SpecialPowers.wrap($("testFrame")).contentDocument;
+  var popup = doc.getElementById("handlersMenuList");
+  isnot(popup, null, "Feed preview should have a handlers popup");
+});
+addLoadEvent(SimpleTest.finish);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/browser/locales/en-US/chrome/browser/browser.dtd b/browser/locales/en-US/chrome/browser/browser.dtd
index 6ba8dc639f0e..5fc63f85bb04 100644
--- a/browser/locales/en-US/chrome/browser/browser.dtd
+++ b/browser/locales/en-US/chrome/browser/browser.dtd
@@ -194,6 +194,8 @@ These should match what Safari and other Apple applications use on OS X Lion. --
 <!ENTITY editThisBookmarkCmd.label "Edit This Bookmark">
 <!ENTITY bookmarkThisPageCmd.commandkey "d">
 
+<!ENTITY subscribeToPageMenupopup.label "Subscribe to This Page">
+<!ENTITY subscribeToPageMenuitem.label "Subscribe to This Page…">
 <!ENTITY addCurPagesCmd.label "Bookmark All Tabs…">
 <!ENTITY showAllBookmarks2.label "Show All Bookmarks">
 <!ENTITY recentBookmarks.label "Recently Bookmarked">
diff --git a/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties b/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
index d7bfec7f7fb4..762068a1688b 100644
--- a/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
+++ b/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
@@ -73,6 +73,9 @@ paste-button.label = Paste
 # LOCALIZATION NOTE(paste-button.tooltiptext2): %S is the keyboard shortcut.
 paste-button.tooltiptext2 = Paste (%S)
 
+feed-button.label = Subscribe
+feed-button.tooltiptext2 = Subscribe to this page
+
 # LOCALIZATION NOTE (characterencoding-button2.label): The \u00ad text at the beginning
 # of the string is used to disable auto hyphenation on the button text when it is displayed
 # in the menu panel.
diff --git a/browser/locales/en-US/chrome/browser/pageInfo.dtd b/browser/locales/en-US/chrome/browser/pageInfo.dtd
index 9126a8f8a97d..39fd57edd0c8 100644
--- a/browser/locales/en-US/chrome/browser/pageInfo.dtd
+++ b/browser/locales/en-US/chrome/browser/pageInfo.dtd
@@ -44,6 +44,9 @@
 <!ENTITY  mediaSaveAs2.accesskey "e">
 <!ENTITY  mediaPreview          "Media Preview:">
 
+<!ENTITY  feedTab               "Feeds">
+<!ENTITY  feedTab.accesskey     "F">
+
 <!ENTITY  permTab               "Permissions">
 <!ENTITY  permTab.accesskey     "P">
 <!ENTITY  permissionsFor        "Permissions for:">
diff --git a/browser/locales/en-US/chrome/browser/pageInfo.properties b/browser/locales/en-US/chrome/browser/pageInfo.properties
index ef73dc820611..6cb2034a5edb 100644
--- a/browser/locales/en-US/chrome/browser/pageInfo.properties
+++ b/browser/locales/en-US/chrome/browser/pageInfo.properties
@@ -38,6 +38,12 @@ generalSize=%S KB (%S bytes)
 generalMetaTag=Meta (1 tag)
 generalMetaTags=Meta (%S tags)
 
+feedRss=RSS
+feedAtom=Atom
+feedXML=XML
+feedSubscribe=Subscribe
+feedSubscribe.accesskey=u
+
 securityNoOwner=This website does not supply ownership information.
 # LOCALIZATION NOTE (securityVisitsNumber):
 # Semi-colon list of plural forms.
diff --git a/browser/modules/Feeds.jsm b/browser/modules/Feeds.jsm
index a2dfc76e75ec..c2127e4a182c 100644
--- a/browser/modules/Feeds.jsm
+++ b/browser/modules/Feeds.jsm
@@ -6,6 +6,13 @@
 
 var EXPORTED_SYMBOLS = [ "Feeds" ];
 
+ChromeUtils.import("resource://gre/modules/Services.jsm");
+
+ChromeUtils.defineModuleGetter(this, "BrowserUtils",
+                               "resource://gre/modules/BrowserUtils.jsm");
+ChromeUtils.defineModuleGetter(this, "BrowserWindowTracker",
+                               "resource:///modules/BrowserWindowTracker.jsm");
+
 var Feeds = {
   // Listeners are added in nsBrowserGlue.js
   receiveMessage(aMessage) {
@@ -18,6 +25,48 @@ var Feeds = {
                                           aMessage.target);
         break;
       }
+
+      case "FeedConverter:addLiveBookmark": {
+        let topWindow = BrowserWindowTracker.getTopWindow();
+        topWindow.PlacesCommandHook.addLiveBookmark(data.spec, data.title)
+                                   .catch(Cu.reportError);
+        break;
+      }
     }
   },
+
+  /**
+   * isValidFeed: checks whether the given data represents a valid feed.
+   *
+   * @param  aLink
+   *         An object representing a feed with title, href and type.
+   * @param  aPrincipal
+   *         The principal of the document, used for security check.
+   * @param  aIsFeed
+   *         Whether this is already a known feed or not, if true only a security
+   *         check will be performed.
+   */
+  isValidFeed(aLink, aPrincipal, aIsFeed) {
+    if (!aLink || !aPrincipal)
+      return false;
+
+    var type = aLink.type.toLowerCase().replace(/^\s+|\s*(?:;.*)?$/g, "");
+    if (!aIsFeed) {
+      aIsFeed = (type == "application/rss+xml" ||
+                 type == "application/atom+xml");
+    }
+
+    if (aIsFeed) {
+      try {
+        let href = Services.io.newURI(aLink.href, aLink.ownerDocument.characterSet);
+        BrowserUtils.urlSecurityCheck(href, aPrincipal,
+                                      Ci.nsIScriptSecurityManager.DISALLOW_INHERIT_PRINCIPAL);
+        return type || "application/rss+xml";
+      } catch (ex) {
+      }
+    }
+
+    return null;
+  },
+
 };
diff --git a/browser/themes/shared/icons/feed.svg b/browser/themes/shared/icons/feed.svg
new file mode 100644
index 000000000000..8235d22ce4d7
--- /dev/null
+++ b/browser/themes/shared/icons/feed.svg
@@ -0,0 +1,6 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
+  <path fill="context-fill" fill-opacity="context-fill-opacity" d="M3.5 10A2.5 2.5 0 1 0 6 12.5 2.5 2.5 0 0 0 3.5 10zM2 1a1 1 0 0 0 0 2 10.883 10.883 0 0 1 11 11 1 1 0 0 0 2 0A12.862 12.862 0 0 0 2 1zm0 4a1 1 0 0 0 0 2 6.926 6.926 0 0 1 7 7 1 1 0 0 0 2 0 8.9 8.9 0 0 0-9-9z"/>
+</svg>
diff --git a/browser/themes/shared/jar.inc.mn b/browser/themes/shared/jar.inc.mn
index 8779d2a1df14..0c98ef738fbd 100644
--- a/browser/themes/shared/jar.inc.mn
+++ b/browser/themes/shared/jar.inc.mn
@@ -148,6 +148,7 @@
   skin/classic/browser/edit-copy.svg                  (../shared/icons/edit-copy.svg)
   skin/classic/browser/edit-cut.svg                   (../shared/icons/edit-cut.svg)
   skin/classic/browser/edit-paste.svg                 (../shared/icons/edit-paste.svg)
+  skin/classic/browser/feed.svg                       (../shared/icons/feed.svg)
   skin/classic/browser/folder.svg                     (../shared/icons/folder.svg)
   skin/classic/browser/forget.svg                     (../shared/icons/forget.svg)
   skin/classic/browser/forward.svg                    (../shared/icons/forward.svg)
diff --git a/browser/themes/shared/toolbarbutton-icons.inc.css b/browser/themes/shared/toolbarbutton-icons.inc.css
index b913e11f19d0..2f15b9fd07b0 100644
--- a/browser/themes/shared/toolbarbutton-icons.inc.css
+++ b/browser/themes/shared/toolbarbutton-icons.inc.css
@@ -212,6 +212,10 @@ toolbar[brighttext] {
   list-style-image: url("chrome://browser/skin/tab.svg");
 }
 
+#feed-button {
+  list-style-image: url("chrome://browser/skin/feed.svg");
+}
+
 #characterencoding-button {
   list-style-image: url("chrome://browser/skin/characterEncoding.svg");
 }
diff --git a/toolkit/content/widgets/browser.xml b/toolkit/content/widgets/browser.xml
index a6f63ebdc5fd..40495a14dfc0 100644
--- a/toolkit/content/widgets/browser.xml
+++ b/toolkit/content/widgets/browser.xml
@@ -516,6 +516,10 @@
         <parameter name="aEvent"/>
         <body>
           <![CDATA[
+            // Delete the feeds cache if we're hiding the topmost page
+            // (as opposed to one of its iframes).
+            if (this.feeds && aEvent.target == this.contentDocument)
+              this.feeds = null;
             if (!this.docShell || !this.fastFind)
               return;
             var tabBrowser = this.getTabBrowser();
@@ -897,6 +901,9 @@
           this._fastFind = null;
           this._webBrowserFind = null;
 
+          // The feeds cache can keep the document inside this browser alive.
+          this.feeds = null;
+
           this.lastURI = null;
 
           if (!this.isRemoteBrowser) {