Remove unused includes from core/html .cpp files

Source/core/html/canvas/WebGLContextGroup.cpp

 /*
  * Copyright (C) 2011 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 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 
 #include "core/html/canvas/WebGLContextGroup.h"
 
 #include "core/html/canvas/WebGLRenderingContext.h"
 #include "core/html/canvas/WebGLSharedObject.h"
-#include "core/platform/graphics/GraphicsContext3D.h"
 
 namespace WebCore {
 
 PassRefPtr<WebGLContextGroup> WebGLContextGroup::create()
 {
     RefPtr<WebGLContextGroup> contextGroup = adoptRef(new WebGLContextGroup());
     return contextGroup.release();
 }
 
 WebGLContextGroup::WebGLContextGroup()
@@ skipping 46 matching lines @@
 
 void WebGLContextGroup::loseContextGroup(WebGLRenderingContext::LostContextMode mode)
 {
     for (HashSet<WebGLRenderingContext*>::iterator it = m_contexts.begin(); it != m_contexts.end(); ++it)
         (*it)->loseContextImpl(mode);
 
     detachAndRemoveAllObjects();
 }
 
 } // namespace WebCore