Update poster code as per https://html.spec.whatwg.org/#show-poster-flag

third_party/WebKit/Source/core/html/HTMLMediaElement.h

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.h b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
index c50d9849c6834ae926ecb763c6e99d210c683290..938d82016452dc180b61e6c13da9b55c3421d87a 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
@@ -280,9 +280,7 @@ protected:
     void didMoveToNewDocument(Document& oldDocument) override;
     virtual KURL posterImageURL() const { return KURL(); }
 
-    enum DisplayMode { Unknown, Poster, Video };
-    DisplayMode displayMode() const { return m_displayMode; }
-    virtual void setDisplayMode(DisplayMode mode) { m_displayMode = mode; }
+    virtual void setShowPoster(bool showPoster) { }
 
     void setControllerInternal(MediaController*);
 
@@ -311,8 +309,6 @@ private:
     // ActiveDOMObject functions.
     void stop() final;
 
-    virtual void updateDisplayState() { }
-
     void setReadyState(ReadyState);
     void setNetworkState(WebMediaPlayer::NetworkState);
 
@@ -520,8 +516,6 @@ private:
     OwnPtr<WebMediaPlayer> m_webMediaPlayer;
     WebLayer* m_webLayer;
 
-    DisplayMode m_displayMode;
-
     RefPtrWillBeMember<HTMLMediaSource> m_mediaSource;
 
     // Cached time value. Only valid when ready state is HAVE_METADATA or