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

Source/core/html/HTMLVideoElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010 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 34 matching lines @@
 #include "platform/graphics/gpu/Extensions3DUtil.h"
 #include "public/platform/WebCanvas.h"
 #include "public/platform/WebGraphicsContext3D.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 inline HTMLVideoElement::HTMLVideoElement(Document& document)
     : HTMLMediaElement(videoTag, document)
+    , m_showPoster(true)
 {
     if (document.settings())
         m_defaultPosterURL = AtomicString(document.settings()->defaultVideoPosterURL());
 }
 
 PassRefPtrWillBeRawPtr<HTMLVideoElement> HTMLVideoElement::create(Document& document)
 {
     RefPtrWillBeRawPtr<HTMLVideoElement> video = adoptRefWillBeNoop(new HTMLVideoElement(document));
     video->ensureUserAgentShadowRoot();
     video->suspendIfNeeded();
@@ skipping 13 matching lines @@
 
 LayoutObject* HTMLVideoElement::createLayoutObject(const ComputedStyle&)
 {
     return new LayoutVideo(this);
 }
 
 void HTMLVideoElement::attach(const AttachContext& context)
 {
     HTMLMediaElement::attach(context);
 
-    updateDisplayState();
+    updateDisplayState(true);
     if (shouldDisplayPosterImage()) {
         if (!m_imageLoader)
             m_imageLoader = HTMLImageLoader::create(this);
         m_imageLoader->updateFromElement();
         if (layoutObject())
             toLayoutImage(layoutObject())->imageResource()->setImageResource(m_imageLoader->image());
     }
 }
 
 void HTMLVideoElement::collectStyleForPresentationAttribute(const QualifiedName& name, const AtomicString& value, MutableStylePropertySet* style)
@@ skipping 11 matching lines @@
     if (name == widthAttr || name == heightAttr)
         return true;
     return HTMLMediaElement::isPresentationAttribute(name);
 }
 
 void HTMLVideoElement::parseAttribute(const QualifiedName& name, const AtomicString& value)
 {
     if (name == posterAttr) {
         // In case the poster attribute is set after playback, don't update the
         // display state, post playback the correct state will be picked up.
-        if (displayMode() < Video || !hasAvailableVideoFrame()) {
-            // Force a poster recalc by setting m_displayMode to Unknown directly before calling updateDisplayState.
-            HTMLMediaElement::setDisplayMode(Unknown);
-            updateDisplayState();
+        if (m_showPoster || !hasAvailableVideoFrame()) {
+            m_showPoster = true;
+            updateDisplayState(true);
         }
         if (!posterImageURL().isEmpty()) {
             if (!m_imageLoader)
                 m_imageLoader = HTMLImageLoader::create(this);
             m_imageLoader->updateFromElement(ImageLoader::UpdateIgnorePreviousError);
         } else {
             if (layoutObject())
                 toLayoutImage(layoutObject())->imageResource()->setImageResource(0);
         }
         // Notify the player when the poster image URL changes.
@@ skipping 24 matching lines @@
 }
 
 const AtomicString HTMLVideoElement::imageSourceURL() const
 {
     const AtomicString& url = getAttribute(posterAttr);
     if (!stripLeadingAndTrailingHTMLSpaces(url).isEmpty())
         return url;
     return m_defaultPosterURL;
 }
 
-void HTMLVideoElement::setDisplayMode(DisplayMode mode)
+void HTMLVideoElement::setShowPoster(bool showPoster)
 {
-    DisplayMode oldMode = displayMode();
     KURL poster = posterImageURL();
 
     if (!poster.isEmpty()) {
         // We have a poster path, but only show it until the user triggers display by playing or seeking and the
         // media engine has something to display.
         // Don't show the poster if there is a seek operation or
         // the video has restarted because of loop attribute
-        if (mode == Video && oldMode == Poster && !hasAvailableVideoFrame())
+        if (!showPoster && m_showPoster && !hasAvailableVideoFrame())
             return;
     }
 
-    HTMLMediaElement::setDisplayMode(mode);
-
-    if (layoutObject() && displayMode() != oldMode)
-        layoutObject()->updateFromElement();
+    if (showPoster != m_showPoster) {
+        m_showPoster = showPoster;
+        if (layoutObject())
+            layoutObject()->updateFromElement();
+    }
 }
 
-void HTMLVideoElement::updateDisplayState()
+void HTMLVideoElement::updateDisplayState(bool forceUpdate)
 {
-    if (posterImageURL().isEmpty())
-        setDisplayMode(Video);
-    else if (displayMode() < Poster)
-        setDisplayMode(Poster);
+    if (posterImageURL().isEmpty()) {
+        setShowPoster(false);
+    } else if (m_showPoster) {
+        if (forceUpdate)
+            m_showPoster = false;
+        setShowPoster(true);
+    }
 }
 
 void HTMLVideoElement::paintCurrentFrame(SkCanvas* canvas, const IntRect& destRect, const SkPaint* paint) const
 {
     if (!webMediaPlayer())
         return;
 
     SkXfermode::Mode mode;
     if (!paint || !SkXfermode::AsMode(paint->getXfermode(), &mode))
         mode = SkXfermode::kSrcOver_Mode;
@@ skipping 109 matching lines @@
 {
     return !isMediaDataCORSSameOrigin(destinationSecurityOrigin);
 }
 
 FloatSize HTMLVideoElement::elementSize() const
 {
     return FloatSize(videoWidth(), videoHeight());
 }
 
 } // namespace blink