Early terminate WebGL markContextChanged calls when appropriate.

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 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 1042 matching lines @@
     ASSERT(drawingBuffer());
     m_drawingBuffer->beginDestruction();
     m_drawingBuffer.clear();
 }
 
 void WebGLRenderingContextBase::markContextChanged(ContentChangeType changeType)
 {
     if (m_framebufferBinding || isContextLost())
         return;
 
-    drawingBuffer()->markContentsChanged();
+    if (!drawingBuffer()->markContentsChanged())
+        return;
 
     LayoutBox* layoutBox = canvas()->layoutBox();
     if (layoutBox && layoutBox->hasAcceleratedCompositing()) {
         m_markedCanvasDirty = true;
         canvas()->clearCopiedImage();
         layoutBox->contentChanged(changeType);
     } else {
         if (!m_markedCanvasDirty) {
             m_markedCanvasDirty = true;
             canvas()->didDraw(FloatRect(FloatPoint(0, 0), FloatSize(clampedCanvasSize())));
@@ skipping 5148 matching lines @@
         contextGL()->PixelStorei(GL_UNPACK_ALIGNMENT, 1);
 }
 
 void WebGLRenderingContextBase::restoreUnpackParameters()
 {
     if (m_unpackAlignment != 1)
         contextGL()->PixelStorei(GL_UNPACK_ALIGNMENT, m_unpackAlignment);
 }
 
 } // namespace blink