Break dependency on core from generated mojom.js files

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) {
+  if (!val.is_valid())
+    return v8::Null(isolate);
   return HandleWrapper::Create(isolate, val.value()).ToV8();
 }
 
 bool Converter<mojo::Handle>::FromV8(v8::Isolate* isolate,
                                      v8::Handle<v8::Value> val,
                                      mojo::Handle* out) {
+  if (val->IsNull()) {
+    *out = mojo::Handle();
+    return true;
+  }
+
   gin::Handle<HandleWrapper> handle;
   if (!Converter<gin::Handle<HandleWrapper> >::FromV8(isolate, val, &handle))
     return false;
 
   *out = handle->get();
   return true;
 }
 
 }  // namespace gin