Bug 1289668 - HTMLMediaElement uses video decoder's frame statistics - r=kamidphish

HTMLVideoElement can expose its thread-safe FrameStatistics object, so that
HTMLMediaElement can access more adequate data for its telemetry, without
having to use an intermediary (and potentially less accurate)
VideoPlaybackQuality object.

This will also help with accessing other/new FrameStatistics members later on.

MozReview-Commit-ID: AT7mEGy0zGr

dom/html/HTMLVideoElement.cpp

@@ -228,6 +228,12 @@ HTMLVideoElement::NotifyOwnerDocumentActivityChangedInternal()
   return pauseElement;
 }
 
+FrameStatistics*
+HTMLVideoElement::GetFrameStatistics()
+{
+  return mDecoder ? &(mDecoder->GetFrameStatistics()) : nullptr;
+}
+
 already_AddRefed<VideoPlaybackQuality>
 HTMLVideoElement::GetVideoPlaybackQuality()
 {