Make WebGL extensions get lost when context is lost.

Source/bindings/v8/custom/V8WebGLRenderingContextCustom.cpp

 /*
  * Copyright (C) 2009 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:
  * 
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 333 matching lines @@
 }
 
 void V8WebGLRenderingContext::getExtensionMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& args)
 {
     WebGLRenderingContext* imp = V8WebGLRenderingContext::toNative(args.Holder());
     if (args.Length() < 1) {
         throwNotEnoughArgumentsError(args.GetIsolate());
         return;
     }
     V8TRYCATCH_FOR_V8STRINGRESOURCE_VOID(V8StringResource<>, name, args[0]);
-    WebGLExtension* extension = imp->getExtension(name);
-    v8SetReturnValue(args, toV8Object(extension, args.Holder(), args.GetIsolate()));
+    RefPtr<WebGLExtension> extension(imp->getExtension(name));
+    v8SetReturnValue(args, toV8Object(extension.get(), args.Holder(), args.GetIsolate()));
 }
 
 void V8WebGLRenderingContext::getFramebufferAttachmentParameterMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& args)
 {
     if (args.Length() != 3) {
         throwNotEnoughArgumentsError(args.GetIsolate());
         return;
     }
 
     ExceptionCode ec = 0;
@@ skipping 457 matching lines @@
 {
     vertexAttribAndUniformHelperf(args, kVertexAttrib3v);
 }
 
 void V8WebGLRenderingContext::vertexAttrib4fvMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& args)
 {
     vertexAttribAndUniformHelperf(args, kVertexAttrib4v);
 }
 
 } // namespace WebCore