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

Source/core/html/HTMLMediaElement.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 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 263 matching lines @@
 
     void parseAttribute(const QualifiedName&, const AtomicString&) override;
     void finishParsingChildren() final;
     bool isURLAttribute(const Attribute&) const override;
     void attach(const AttachContext& = AttachContext()) override;
 
     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 DisplayMode displayMode() const { return Unknown; }

[philipj_slow, 2015/08/18 08:24:48]

Do these need to be virtual and on HTMLMediaElement at all? If there are very
few call sites, maybe they can just cast to HTMLVideoElement instead?

[Srirama, 2015/08/18 08:58:26]

But our intention is to make sure these functions won't execute incase of Audio
element. So if we move these functions completely to HTMLVideoElement, it will
again be same as the current code right. Or you want me to move them and then
add VideoElement check at the call site in HTMLMediaElement?

[philipj_slow, 2015/08/18 09:10:28]

It looks like the displayMode() getter is only used in HTMLVideoElement, so at
least that doesn't need to be virtual.

There are three call sites to setDisplayMode() in HTMLMediaElement, and I think
it almost corresponds to https://html.spec.whatwg.org/#show-poster-flag in the
spec.

So here's an idea: introduce the show poster flag and update it per spec, then
perhaps the setShowPoster() call can be virtual so that HTMLVideoElement does
something extra before or after if needed.

+    virtual void setDisplayMode(DisplayMode mode) { }
 
     void setControllerInternal(MediaController*);
 
 private:
     void resetMediaPlayerAndMediaSource();
 
     bool alwaysCreateUserAgentShadowRoot() const final { return true; }
     bool areAuthorShadowsAllowed() const final { return false; }
 
     bool supportsFocus() const final;
@@ skipping 205 matching lines @@
         // The load is deferred, and waiting for the task to set the
         // delaying-the-load-event flag, after which the load will be executed.
         ExecuteOnStopDelayingLoadEventTask
     };
     DeferredLoadState m_deferredLoadState;
     Timer<HTMLMediaElement> m_deferredLoadTimer;
 
     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
     // higher, otherwise the current time is assumed to be zero.
     mutable double m_cachedTime;
 
     double m_fragmentEndTime;
 
     typedef unsigned PendingActionFlags;
     PendingActionFlags m_pendingActionFlags;
@@ skipping 106 matching lines @@
 inline bool isHTMLMediaElement(const HTMLElement& element)
 {
     return isHTMLAudioElement(element) || isHTMLVideoElement(element);
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLMediaElement);
 
 } // namespace blink
 
 #endif // HTMLMediaElement_h