Enable smooth transition when show/hide media remoting interstitial.

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

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MediaRemotingInterstitial_h
 #define MediaRemotingInterstitial_h
 
 #include "core/html/HTMLDivElement.h"
 
 namespace blink {
@@ skipping 16 matching lines @@
 // |    (-internal-media-remoting-cast-text-message)
 // \-MediaRemotingExitButtonElement
 //      (-internal-media-remoting-disable-button)
 class MediaRemotingInterstitial final : public HTMLDivElement {
  public:
   explicit MediaRemotingInterstitial(HTMLVideoElement&);
 
   // Show/Hide Media Remoting interstitial.
   void Show();
   void Hide();
+
   void OnPosterImageChanged();
 
   HTMLVideoElement& GetVideoElement() const { return *video_element_; }
 
   DECLARE_VIRTUAL_TRACE();
 
  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_;
   Member<MediaRemotingCastIconElement> cast_icon_;
   Member<MediaRemotingCastMessageElement> cast_text_message_;
 };
 
 }  // namespace
 
 #endif  // MediaRemotingInterstitial_h