Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/WebGLExtension.cpp

 /*
  * Copyright (C) 2010 Google 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
@@ skipping 13 matching lines @@
  */
 
 #include "config.h"
 
 #include "core/html/canvas/WebGLExtension.h"
 
 namespace WebCore {
 
 WebGLExtension::WebGLExtension(WebGLRenderingContext* context)
     : m_context(context)
+    , m_lost(false)
 {
 }
 
 WebGLExtension::~WebGLExtension()
 {
 }
 
 } // namespace WebCore