Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/EXTFragDepth.cpp

 /*
  * Copyright (C) 2013 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 29 matching lines @@
 
 EXTFragDepth::~EXTFragDepth()
 {
 }
 
 WebGLExtension::ExtensionName EXTFragDepth::getName() const
 {
     return EXTFragDepthName;
 }
 
-PassOwnPtr<EXTFragDepth> EXTFragDepth::create(WebGLRenderingContext* context)
+PassRefPtr<EXTFragDepth> EXTFragDepth::create(WebGLRenderingContext* context)
 {
-    return adoptPtr(new EXTFragDepth(context));
+    return adoptRef(new EXTFragDepth(context));
 }
 
 bool EXTFragDepth::supported(WebGLRenderingContext* context)
 {
     Extensions3D* extensions = context->graphicsContext3D()->getExtensions();
     return extensions->supports("GL_EXT_frag_depth");
 }
 
 const char* EXTFragDepth::getExtensionName()
 {
     return "EXT_frag_depth";
 }
 
 } // namespace WebCore