Enable smooth transition when show/hide media remoting interstitial.

third_party/WebKit/Source/core/html/HTMLVideoElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 474 matching lines @@
     return ScriptPromise();
   if (!ImageBitmap::IsResizeOptionValid(options, exception_state))
     return ScriptPromise();
   return ImageBitmapSource::FulfillImageBitmap(
       script_state, ImageBitmap::Create(
                         this, crop_rect,
                         event_target.ToLocalDOMWindow()->document(), options));
 }
 
 void HTMLVideoElement::MediaRemotingStarted() {
-  DCHECK_EQ(media_remoting_status_, MediaRemotingStatus::kNotStarted);
+  DCHECK(media_remoting_status_ == MediaRemotingStatus::kNotStarted);
   media_remoting_status_ = MediaRemotingStatus::kStarted;
   if (!remoting_interstitial_) {
     remoting_interstitial_ = new MediaRemotingInterstitial(*this);
     ShadowRoot& shadow_root = EnsureUserAgentShadowRoot();
     shadow_root.InsertBefore(remoting_interstitial_, shadow_root.FirstChild());
     HTMLMediaElement::AssertShadowRootChildren(shadow_root);
   }
   remoting_interstitial_->Show();
 }
 
 void HTMLVideoElement::MediaRemotingStopped() {
-  if (media_remoting_status_ != MediaRemotingStatus::kDisabled)
-    media_remoting_status_ = MediaRemotingStatus::kNotStarted;
+  // Early return because this was already called when media remoting was
+  // disabled.
+  if (media_remoting_status_ == MediaRemotingStatus::kDisabled)
+    return;
+  DCHECK(media_remoting_status_ == MediaRemotingStatus::kStarted);
   DCHECK(remoting_interstitial_);
+  media_remoting_status_ = MediaRemotingStatus::kNotStarted;
   remoting_interstitial_->Hide();
 }
 
 void HTMLVideoElement::DisableMediaRemoting() {
   if (GetWebMediaPlayer())
     GetWebMediaPlayer()->RequestRemotePlaybackDisabled(true);
   media_remoting_status_ = MediaRemotingStatus::kDisabled;
   MediaRemotingStopped();

[whywhat, 2017/05/18 16:31:36]

This line seems to be either out of order or obsolete as MediaRemotingStopped
will now early return due to the added check, won't it?

[xjz, 2017/05/18 18:37:23]

Yes, you are right. This call does nothing. With a second thought, I think the
MediaRemotingStopped() call here and the added early return can be removed. Will
upload a quick fix soon. Thanks for catching this!

 }
 
 }  // namespace blink