Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/WebGLCompressedTextureS3TC.h

 /*
  * Copyright (C) 2012 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 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.
  */
 
 #ifndef WebGLCompressedTextureS3TC_h
 #define WebGLCompressedTextureS3TC_h
 
 #include "bindings/v8/ScriptWrappable.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/html/canvas/WebGLExtension.h"
-#include "wtf/PassOwnPtr.h"
+#include "wtf/PassRefPtr.h"
 
 namespace WebCore {
 
 class WebGLTexture;
 
 class WebGLCompressedTextureS3TC : public WebGLExtension, public ScriptWrappable {
 public:
-    static PassOwnPtr<WebGLCompressedTextureS3TC> create(WebGLRenderingContext*);
+    static PassRefPtr<WebGLCompressedTextureS3TC> create(WebGLRenderingContext*);
     static bool supported(WebGLRenderingContext*);
     static const char* getExtensionName();
 
     virtual ~WebGLCompressedTextureS3TC();
     virtual ExtensionName getName() const;
 
 private:
     WebGLCompressedTextureS3TC(WebGLRenderingContext*);
 };
 
 } // namespace WebCore
 
 #endif // WebGLCompressedTextureS3TC_h