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

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

Index: third_party/WebKit/Source/core/html/HTMLVideoElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLVideoElement.h b/third_party/WebKit/Source/core/html/HTMLVideoElement.h
index 056e560e787dbdf00b450dcf6b7b23623ba79614..c8b2c0e99b79cc268fd86e22b11d427917ce5135 100644
--- a/third_party/WebKit/Source/core/html/HTMLVideoElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLVideoElement.h
@@ -71,7 +71,7 @@ public:
     // Used by WebGL to do GPU-GPU textures copy if possible.
     bool copyVideoTextureToPlatformTexture(WebGraphicsContext3D*, Platform3DObject texture, GLenum internalFormat, GLenum type, bool premultiplyAlpha, bool flipY);
 
-    bool shouldDisplayPosterImage() const { return displayMode() == Poster; }
+    bool shouldDisplayPosterImage() const { return m_showPoster; }
 
     bool hasAvailableVideoFrame() const;
 
@@ -99,10 +99,12 @@ private:
     bool isURLAttribute(const Attribute&) const override;
     const AtomicString imageSourceURL() const override;
 
-    void updateDisplayState() override;
     void didMoveToNewDocument(Document& oldDocument) override;
-    void setDisplayMode(DisplayMode) override;
+    void setShowPoster(bool) override;
 
+    // This flag is used to control when the user agent is to show a
+    // poster frame for a video element instead of showing the video contents.
+    bool m_showPoster : 1;
     OwnPtrWillBeMember<HTMLImageLoader> m_imageLoader;
 
     AtomicString m_defaultPosterURL;