Bug 1346116 part 2 - consider a video is in-tree or not in the suspend-video-decoding policy; r=jwwang

We never suspend videos that is NOT in-tree because we found that, according to the Telemetry data, most (>70%) videos
which are used as the argument of drawImage() are not in-tree. So, by preventing suspending not-in-tree videos, we should
be able to alleviate the pain of not able to resume video decoders synchronously.

MozReview-Commit-ID: 8eqs0pHZLIt

--HG--
extra : rebase_source : 964c0047753696cad2e40bcf74c2b8ee9faccdea
extra : source : 93c38caa15b1a29f8f1e8e6d3a5e859f97bc1aae

dom/html/HTMLMediaElement.cpp

@@ -7404,7 +7404,8 @@ HTMLMediaElement::NotifyDecoderActivityChanges() const
 {
   if (mDecoder) {
     mDecoder->NotifyOwnerActivityChanged(!IsHidden(),
-                                         mVisibilityState == Visibility::APPROXIMATELY_VISIBLE);
+                                         mVisibilityState == Visibility::APPROXIMATELY_VISIBLE,
+                                         IsInUncomposedDoc());
   }
 }
 

dom/media/MediaDecoder.cpp

@@ -298,11 +298,12 @@ MediaDecoder::ResourceCallback::NotifyBytesConsumed(int64_t aBytes,
 
 void
 MediaDecoder::NotifyOwnerActivityChanged(bool aIsDocumentVisible,
-                                         bool aIsElementVisible)
+                                         bool aIsElementVisible,
+                                         bool aIsElementInTree)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_DIAGNOSTIC_ASSERT(!IsShutdown());
-  SetElementVisibility(aIsDocumentVisible, aIsElementVisible);
+  SetElementVisibility(aIsDocumentVisible, aIsElementVisible, aIsElementInTree);
 
   NotifyCompositor();
 }
@@ -397,6 +398,7 @@ MediaDecoder::MediaDecoder(MediaDecoderOwner* aOwner)
   , mFiredMetadataLoaded(false)
   , mIsDocumentVisible(false)
   , mIsElementVisible(false)
+  , mIsElementInTree(false)
   , mForcedHidden(false)
   , mHasSuspendTaint(false)
   , INIT_MIRROR(mStateMachineIsShutdown, true)
@@ -1308,11 +1310,13 @@ MediaDecoder::NotifyCompositor()
 
 void
 MediaDecoder::SetElementVisibility(bool aIsDocumentVisible,
-                                   bool aIsElementVisible)
+                                   bool aIsElementVisible,
+                                   bool aIsElementInTree)
 {
   MOZ_ASSERT(NS_IsMainThread());
   mIsDocumentVisible = aIsDocumentVisible;
   mIsElementVisible = aIsElementVisible;
+  mIsElementInTree = aIsElementInTree;
   UpdateVideoDecodeMode();
 }
 
@@ -1346,6 +1350,12 @@ MediaDecoder::UpdateVideoDecodeMode()
     return;
   }
 
+  // Don't suspend elements that is not in tree.
+  if (!mIsElementInTree) {
+    mDecoderStateMachine->SetVideoDecodeMode(VideoDecodeMode::Normal);
+    return;
+  }
+
   // If mForcedHidden is set, suspend the video decoder anyway.
   if (mForcedHidden) {
     mDecoderStateMachine->SetVideoDecodeMode(VideoDecodeMode::Suspend);

dom/media/MediaDecoder.h

@@ -190,7 +190,8 @@ public:
 
   // Notify activity of the decoder owner is changed.
   virtual void NotifyOwnerActivityChanged(bool aIsDocumentVisible,
-                                          bool aIsElementVisible);
+                                          bool aIsElementVisible,
+                                          bool aIsElementInTree);
 
   // Pause video playback.
   virtual void Pause();
@@ -373,7 +374,8 @@ private:
 
   // Called from HTMLMediaElement when owner document activity changes
   virtual void SetElementVisibility(bool aIsDocumentVisible,
-                                    bool aIsElementVisible);
+                                    bool aIsElementVisible,
+                                    bool aIsElementInTree);
 
   // Force override the visible state to hidden.
   // Called from HTMLMediaElement when testing of video decode suspend from mochitests.
@@ -721,9 +723,12 @@ protected:
   // Tracks the visibility status of owner element's document.
   bool mIsDocumentVisible;
 
-  // Tracks the visibliity status of owner element.
+  // Tracks the visibility status of owner element.
   bool mIsElementVisible;
 
+  // Tracks the owner is in-tree or not.
+  bool mIsElementInTree;
+
   // If true, forces the decoder to be considered hidden.
   bool mForcedHidden;