b=478982 Gecko users may need to prevent autoplay for video/audio content in messages r=roc,dolske sr=roc

content/html/content/public/nsHTMLMediaElement.h

@@ -337,6 +337,10 @@ protected:
   // is a result of the autoplay attribute.
   PRPackedBool mAutoplaying;
 
+  // Indicates whether |autoplay| will actually autoplay based on the pref 
+  // media.autoplay.enabled
+  PRPackedBool mAutoplayEnabled;
+
   // Playback of the video is paused either due to calling the
   // 'Pause' method, or playback not yet having started.
   PRPackedBool mPaused;

content/html/content/src/nsHTMLMediaElement.cpp

@@ -252,6 +252,14 @@ NS_IMPL_URI_ATTR(nsHTMLMediaElement, Src, src)
 NS_IMPL_BOOL_ATTR(nsHTMLMediaElement, Controls, controls)
 NS_IMPL_BOOL_ATTR(nsHTMLMediaElement, Autoplay, autoplay)
 
+/* readonly attribute nsIDOMHTMLMediaElement mozAutoplayEnabled; */
+NS_IMETHODIMP nsHTMLMediaElement::GetMozAutoplayEnabled(PRBool *aAutoplayEnabled)
+{
+  *aAutoplayEnabled = mAutoplayEnabled;
+
+  return NS_OK;
+}
+
 /* readonly attribute nsIDOMHTMLMediaError error; */
 NS_IMETHODIMP nsHTMLMediaElement::GetError(nsIDOMHTMLMediaError * *aError)
 {
@@ -619,6 +627,7 @@ nsHTMLMediaElement::nsHTMLMediaElement(nsINodeInfo *aNodeInfo, PRBool aFromParse
     mBegun(PR_FALSE),
     mLoadedFirstFrame(PR_FALSE),
     mAutoplaying(PR_TRUE),
+    mAutoplayEnabled(PR_TRUE),
     mPaused(PR_TRUE),
     mMuted(PR_FALSE),
     mIsDoneAddingChildren(!aFromParser),
@@ -720,11 +729,17 @@ nsresult nsHTMLMediaElement::SetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
   return rv;
 }
 
+static PRBool IsAutoplayEnabled()
+{
+  return nsContentUtils::GetBoolPref("media.autoplay.enabled");
+}
+
 nsresult nsHTMLMediaElement::BindToTree(nsIDocument* aDocument, nsIContent* aParent,
                                         nsIContent* aBindingParent,
                                         PRBool aCompileEventHandlers)
 {
   mIsBindingToTree = PR_TRUE;
+  mAutoplayEnabled = IsAutoplayEnabled();
   nsresult rv = nsGenericHTMLElement::BindToTree(aDocument, 
                                                  aParent, 
                                                  aBindingParent, 
@@ -1291,7 +1306,8 @@ void nsHTMLMediaElement::ChangeReadyState(nsMediaReadyState aState)
       }
       if (mAutoplaying &&
           mPaused &&
-          HasAttr(kNameSpaceID_None, nsGkAtoms::autoplay)) {
+          HasAttr(kNameSpaceID_None, nsGkAtoms::autoplay) &&
+          mAutoplayEnabled) {
         mPaused = PR_FALSE;
         if (mDecoder) {
           mDecoder->Play();

dom/public/idl/html/nsIDOMHTMLMediaElement.idl

@@ -56,7 +56,7 @@
 #endif
 %}
 
-[scriptable, uuid(c19f04dc-f09a-4b1f-b354-af65a12aa8bc)]
+[scriptable, uuid(debed306-1a49-4af8-b10a-8452978a2db1)]
 interface nsIDOMHTMLMediaElement : nsIDOMHTMLElement
 {
   // error state
@@ -87,6 +87,7 @@ interface nsIDOMHTMLMediaElement : nsIDOMHTMLElement
   readonly attribute float duration;
   readonly attribute boolean paused;
   readonly attribute boolean ended;
+  readonly attribute boolean mozAutoplayEnabled;
            attribute boolean autoplay;
   void play();
   void pause();

modules/libpref/src/init/all.js

@@ -143,6 +143,9 @@ pref("media.ogg.enabled", true);
 pref("media.wave.enabled", true);
 #endif
 
+// Whether to autostart a media element with an |autoplay| attribute
+pref("media.autoplay.enabled", true);
+
 // 0 = Off, 1 = Full, 2 = Tagged Images Only. 
 // See eCMSMode in gfx/thebes/public/gfxPlatform.h
 pref("gfx.color_management.mode", 2);

toolkit/content/widgets/videocontrols.xml

@@ -272,7 +272,8 @@
                     // Suppress fading out the controls until the video has rendered
                     // its first frame. But since autoplay videos start off with no
                     // controls, let them fade-out so the controls don't get stuck on.
-                    if (!this.firstFrameShown && !isMouseOver && !this.video.autoplay)
+                    if (!this.firstFrameShown && !isMouseOver &&
+                        !(this.video.autoplay && this.video.mozAutoplayEnabled))
                         return;
 
                     // If we're already fading towards the desired state (or are
@@ -403,7 +404,7 @@
             // go ahead and reveal the controls now, so they're an obvious user cue.
             //
             // (Note: the |controls| attribute is already handled via layout/style/html.css)
-            if (!video.autoplay || !this.Utils.dynamicControls) {
+            if (!(video.autoplay && video.mozAutoplayEnabled) || !this.Utils.dynamicControls) {
                 this.Utils.controlBar.style.visibility = "visible";
                 this.Utils.controlBar.style.opacity = 1.0;
                 this.Utils.controlsVisible = true;