Bug 1282484 - Add a mechanism to control plugin fallback content. r=qDot

MozReview-Commit-ID: Lt4tOdFdQzN

dom/base/nsObjectLoadingContent.cpp

@@ -109,6 +109,7 @@ static NS_DEFINE_CID(kAppShellCID, NS_APPSHELL_CID);
 static const char *kPrefJavaMIME = "plugin.java.mime";
 static const char *kPrefYoutubeRewrite = "plugins.rewrite_youtube_embeds";
 static const char *kPrefBlockURIs = "browser.safebrowsing.blockedURIs.enabled";
+static const char *kPrefFavorFallbackMode = "plugins.favorfallback.mode";
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -3372,11 +3373,22 @@ nsObjectLoadingContent::ShouldPlay(FallbackType &aReason, bool aIgnoreCurrentTyp
     }
     switch (permission) {
     case nsIPermissionManager::ALLOW_ACTION:
+      if (PreferFallback(false /* isPluginClickToPlay */)) {
+        aReason = eFallbackAlternate;
+        return false;
+      }
+
       return true;
     case nsIPermissionManager::DENY_ACTION:
       aReason = eFallbackDisabled;
       return false;
     case nsIPermissionManager::PROMPT_ACTION:
+      if (PreferFallback(true /* isPluginClickToPlay */)) {
+        // False is already returned in this case, but
+        // it's important to correctly set aReason too.
+        aReason = eFallbackAlternate;
+      }
+
       return false;
     case nsIPermissionManager::UNKNOWN_ACTION:
       break;
@@ -3392,6 +3404,11 @@ nsObjectLoadingContent::ShouldPlay(FallbackType &aReason, bool aIgnoreCurrentTyp
     return false;
   }
 
+  if (PreferFallback(enabledState == nsIPluginTag::STATE_CLICKTOPLAY)) {
+    aReason = eFallbackAlternate;
+    return false;
+  }
+
   switch (enabledState) {
   case nsIPluginTag::STATE_ENABLED:
     return true;
@@ -3401,6 +3418,48 @@ nsObjectLoadingContent::ShouldPlay(FallbackType &aReason, bool aIgnoreCurrentTyp
   MOZ_CRASH("Unexpected enabledState");
 }
 
+bool
+nsObjectLoadingContent::FavorFallbackMode(bool aIsPluginClickToPlay) {
+  if (!IsFlashMIME(mContentType)) {
+    return false;
+  }
+
+  nsCString prefString;
+  if (NS_SUCCEEDED(Preferences::GetCString(kPrefFavorFallbackMode, &prefString))) {
+    if (aIsPluginClickToPlay &&
+        prefString.EqualsLiteral("follow-ctp")) {
+      return true;
+    }
+
+    if (prefString.EqualsLiteral("always")) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool
+nsObjectLoadingContent::HasGoodFallback() {
+  nsCOMPtr<nsIContent> thisContent =
+  do_QueryInterface(static_cast<nsIImageLoadingContent*>(this));
+  NS_ASSERTION(thisContent, "must be a content");
+
+  if (!thisContent->IsHTMLElement(nsGkAtoms::object) ||
+      mContentType.IsEmpty()) {
+    return false;
+  }
+
+  // xxx to be filled
+
+  return false;
+}
+
+bool
+nsObjectLoadingContent::PreferFallback(bool aIsPluginClickToPlay) {
+  return FavorFallbackMode(aIsPluginClickToPlay) && HasGoodFallback();
+}
+
 nsIDocument*
 nsObjectLoadingContent::GetContentDocument(nsIPrincipal& aSubjectPrincipal)
 {

dom/base/nsObjectLoadingContent.h

@@ -460,6 +460,32 @@ class nsObjectLoadingContent : public nsImageLoadingContent
      */
     bool ShouldPlay(FallbackType &aReason, bool aIgnoreCurrentType);
 
+    /**
+     * This method tells if the fallback content should be attempted to be used
+     * over the original object content.
+     * It will look at prefs and this plugin's CTP state to make a decision.
+     *
+     * NOTE that this doesn't say whether the fallback _will_ be used, only whether
+     * we should look into it to possibly use it. The final answer will be
+     * given by the PreferFallback method.
+     *
+     * @param aIsPluginClickToPlay Whether this object instance is CTP.
+     */
+    bool FavorFallbackMode(bool aIsPluginClickToPlay);
+
+    /**
+     * Whether the page has provided good fallback content to this object.
+     */
+    bool HasGoodFallback();
+
+    /**
+     * This method tells the final answer on whether this object's fallback
+     * content should be used instead of the original plugin content.
+     *
+     * @param aIsPluginClickToPlay Whether this object instance is CTP.
+     */
+    bool PreferFallback(bool aIsPluginClickToPlay);
+
     /*
      * Helper to check if mBaseURI can be used by java as a codebase
      */

modules/libpref/init/all.js

@@ -2824,6 +2824,14 @@ pref("plugin.sessionPermissionNow.intervalInMinutes", 60);
 // to allow it persistently.
 pref("plugin.persistentPermissionAlways.intervalInDays", 90);
 
+// This pref can take 3 possible string values:
+// "always"     - always use favor fallback mode
+// "follow-ctp" - activate if ctp is active for the given
+//                plugin object (could be due to a plugin-wide
+//                setting or a site-specific setting)
+// "never"      - never use favor fallback mode
+pref("plugins.favorfallback.mode", "never");
+
 // Set IPC timeouts for plugins and tabs, except in leak-checking and
 // dynamic analysis builds.  (NS_FREE_PERMANENT_DATA is C++ only, so
 // approximate its definition here.)