Enable smooth transition when show/hide media remoting interstitial.

third_party/WebKit/Source/core/html/shadow/MediaRemotingInterstitial.h

Index: third_party/WebKit/Source/core/html/shadow/MediaRemotingInterstitial.h
diff --git a/third_party/WebKit/Source/core/html/shadow/MediaRemotingInterstitial.h b/third_party/WebKit/Source/core/html/shadow/MediaRemotingInterstitial.h
index 0baaa2bdd0039f110dfbc97fce57910d4e857837..75a0d4d4c9b0af31d25657d20616572c5127e9bb 100644
--- a/third_party/WebKit/Source/core/html/shadow/MediaRemotingInterstitial.h
+++ b/third_party/WebKit/Source/core/html/shadow/MediaRemotingInterstitial.h
@@ -34,6 +34,7 @@ class MediaRemotingInterstitial final : public HTMLDivElement {
   // Show/Hide Media Remoting interstitial.
   void Show();
   void Hide();
+
   void OnPosterImageChanged();
 
   HTMLVideoElement& GetVideoElement() const { return *video_element_; }
@@ -43,7 +44,15 @@ class MediaRemotingInterstitial final : public HTMLDivElement {
  private:
   // Node override.
   bool IsMediaRemotingInterstitial() const override { return true; }
+  void DidMoveToNewDocument(Document&) override;
+
+  void ToggleInterstitialTimerFired(TimerBase*);
+
+  // Indicates whether the interstitial should be visible. It is set/changed
+  // when SHow()/Hide() is called.
+  bool should_be_visible_ = false;
 
+  TaskRunnerTimer<MediaRemotingInterstitial> toggle_insterstitial_timer_;
   Member<HTMLVideoElement> video_element_;
   Member<HTMLImageElement> background_image_;
   Member<MediaRemotingExitButtonElement> exit_button_;