avoid poster flicker during video looping or random seek operation

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 149 matching lines @@
 }
 
 void HTMLVideoElement::setDisplayMode(DisplayMode mode)
 {
     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.
-        if (mode == Video && !hasAvailableVideoFrame())
+        // 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())
             mode = PosterWaitingForVideo;
     }
 
     HTMLMediaElement::setDisplayMode(mode);
 
     if (renderer() && displayMode() != oldMode)
         renderer()->updateFromElement();
 }
 
 void HTMLVideoElement::updateDisplayState()
@@ skipping 116 matching lines @@
 {
     return !hasSingleSecurityOrigin() || (!(player() && player()->didPassCORSAccessCheck()) && destinationSecurityOrigin->taintsCanvas(currentSrc()));
 }
 
 FloatSize HTMLVideoElement::sourceSize() const
 {
     return FloatSize(videoWidth(), videoHeight());
 }
 
 }