Bug 1350821 - Notify the mediaElement to render subtitle when the mCaption was created or re-created. r=rillian

MozReview-Commit-ID: 3RM7u8jumT9

--HG--
extra : rebase_source : 2a3ed8f304ac8fdf9c0cc897e2f70bd2d23e8101

layout/generic/nsVideoFrame.cpp

@@ -138,6 +138,7 @@ nsVideoFrame::CreateAnonymousContent(nsTArray<ContentInfo>& aElements)
 
     if (!aElements.AppendElement(mCaptionDiv))
       return NS_ERROR_OUT_OF_MEMORY;
+    UpdateTextTrack();
   }
 
   // Set up "videocontrols" XUL element which will be XBL-bound to the
@@ -776,3 +777,11 @@ bool nsVideoFrame::HasVideoData()
   element->GetVideoSize(&size);
   return size != nsIntSize(0,0);
 }
+
+void nsVideoFrame::UpdateTextTrack()
+{
+  HTMLMediaElement* element = static_cast<HTMLMediaElement*>(GetContent());
+  if (element) {
+    element->NotifyCueDisplayStatesChanged();
+  }
+}

layout/generic/nsVideoFrame.h

@@ -128,6 +128,9 @@ protected:
   // elements, not for frames for audio elements.
   void UpdatePosterSource(bool aNotify);
 
+  // Notify the mediaElement that the mCaptionDiv was created.
+  void UpdateTextTrack();
+
   virtual ~nsVideoFrame();
 
   // Anonymous child which is bound via XBL to the video controls.