Bug 886496 - When doing lazy tab restoration, set the <browser>s in question to display:none until restored r=bnicholson

mobile/android/chrome/content/MemoryObserver.js

@@ -50,6 +50,7 @@ var MemoryObserver = {
     browser.__SS_data = data;
     browser.__SS_extdata = extra;
     browser.__SS_restore = true;
+    browser.setAttribute("pending", "true");
   },
 
   gc: function() {

mobile/android/components/SessionStore.js

@@ -418,6 +418,7 @@ SessionStore.prototype = {
         this._restoreHistory(data, aBrowser.sessionHistory);
 
       delete aBrowser.__SS_restore;
+      aBrowser.removeAttribute("pending");
     }
 
     this.saveStateDelayed();
@@ -861,10 +862,12 @@ SessionStore.prototype = {
       if (window.BrowserApp.selectedTab == tab) {
         this._restoreHistory(tabData, tab.browser.sessionHistory);
         delete tab.browser.__SS_restore;
+        tab.browser.removeAttribute("pending");
       } else {
         // Make sure the browser has its session data for the delay reload
         tab.browser.__SS_data = tabData;
         tab.browser.__SS_restore = true;
+        tab.browser.setAttribute("pending", "true");
       }
 
       tab.browser.__SS_extdata = tabData.extData;

mobile/android/themes/core/browser.css

@@ -2,33 +2,12 @@
  * 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/. */
 
-%filter substitution
-%include defines.inc
-
-/* content scrollbars */
-.scroller {
-  opacity: 0;
-  background-color: rgba(0, 0, 0, 0.4) !important;
-  -moz-border-top-colors: none !important;
-  -moz-border-bottom-colors: none !important;
-  -moz-border-right-colors: none !important;
-  -moz-border-left-colors: none !important;
-  border-radius: @border_radius_tiny@;
-  border: @border_width_tiny@ solid rgba(255, 255, 255, 0.4) !important;
-}
-
-.scroller[panning="true"] {
-  opacity: 1;
-}
-
-.scroller[orient="vertical"] {
-  min-width: @scroller_thickness@;
-  width: @scroller_thickness@;
-  min-height: @scroller_minimum@;
-}
-
-.scroller[orient="horizontal"] {
-  min-height: @scroller_thickness@;
-  height: @scroller_thickness@;
-  min-width: @scroller_minimum@;
+/**
+ * Optimization for tabs that are restored lazily. We can save a good amount of
+ * memory that to-be-restored tabs would otherwise consume simply by setting
+ * their browsers to 'display: none' as that will prevent them from having to
+ * create a presentation and the like.
+ */
+browser[pending] {
+  display: none;
 }

mobile/android/themes/core/jar.mn

@@ -20,7 +20,7 @@ chrome.jar:
 * skin/aboutPrivateBrowsing.css             (aboutPrivateBrowsing.css)
   skin/aboutReader.css                      (aboutReader.css)
   skin/aboutSupport.css                     (aboutSupport.css)
-* skin/browser.css                          (browser.css)
+  skin/browser.css                          (browser.css)
 * skin/content.css                          (content.css)
   skin/config.css                           (config.css)
   skin/touchcontrols.css                    (touchcontrols.css)