Change mojo JS bindings to expose a handle object, which is Closed when garbage

mojo/bindings/js/handle.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/bindings/js/handle.h"
 
 namespace gin {
 
+gin::WrapperInfo HandleWrapper::kWrapperInfo = { gin::kEmbedderNativeGin };
+
+HandleWrapper::HandleWrapper(MojoHandle handle)
+    : handle_(mojo::Handle(handle)) {
+}
+
+HandleWrapper::~HandleWrapper() {
+}
+
 v8::Handle<v8::Value> Converter<mojo::Handle>::ToV8(v8::Isolate* isolate,
                                                     const mojo::Handle& val) {
-  return Converter<MojoHandle>::ToV8(isolate, val.value());
+  return HandleWrapper::Create(isolate, val.value()).ToV8();
 }
 
 bool Converter<mojo::Handle>::FromV8(v8::Isolate* isolate,
                                      v8::Handle<v8::Value> val,
                                      mojo::Handle* out) {
-  return Converter<MojoHandle>::FromV8(isolate, val, out->mutable_value());
+  gin::Handle<HandleWrapper> handle;
+  if (!Converter<gin::Handle<HandleWrapper> >::FromV8(isolate, val, &handle))
+    return false;
+
+  *out = handle->get();
+  return true;
 }
 
 }  // namespace gin