Two fixes for mojo JS bindings

mojo/bindings/js/waiting_callback.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/waiting_callback.h"
 
 #include "gin/per_context_data.h"
+#include "mojo/public/cpp/environment/default_async_waiter.h"
 
 namespace mojo {
 namespace js {
 
 namespace {
 
 v8::Handle<v8::String> GetHiddenPropertyName(v8::Isolate* isolate) {
   return gin::StringToSymbol(isolate, "::mojo::js::WaitingCallback");
 }
 
 }  // namespace
 
 gin::WrapperInfo WaitingCallback::kWrapperInfo = { gin::kEmbedderNativeGin };
 
+// static
+gin::Handle<WaitingCallback> WaitingCallback::Create(
+    v8::Isolate* isolate,
+    v8::Handle<v8::Function> callback,
+    mojo::Handle handle,
+    MojoWaitFlags flags) {
+  gin::Handle<WaitingCallback> waiting_callback =
+      gin::CreateHandle(isolate, new WaitingCallback(isolate, callback));
+  MojoAsyncWaiter* waiter = GetDefaultAsyncWaiter();
+  waiting_callback->wait_id_ = waiter->AsyncWait(
+      waiter,
+      handle.value(),
+      flags,
+      MOJO_DEADLINE_INDEFINITE,
+      &WaitingCallback::CallOnHandleReady,
+      waiting_callback.get());
+  return waiting_callback;
+}
+
+void WaitingCallback::Cancel() {
+  if (!wait_id_)
+    return;
+
+  MojoAsyncWaiter* waiter = GetDefaultAsyncWaiter();
+  waiter->CancelWait(waiter, wait_id_);
+  wait_id_ = 0;
+}
+
 WaitingCallback::WaitingCallback(v8::Isolate* isolate,
                                  v8::Handle<v8::Function> callback)
       : wait_id_() {
   v8::Handle<v8::Context> context = isolate->GetCurrentContext();
   runner_ = gin::PerContextData::From(context)->runner()->GetWeakPtr();
   GetWrapper(isolate)->SetHiddenValue(GetHiddenPropertyName(isolate), callback);
 }
 
 WaitingCallback::~WaitingCallback() {
-  DCHECK(!wait_id_) << "Waiting callback was destroyed before being cancelled.";
-}
-
-gin::Handle<WaitingCallback> WaitingCallback::Create(
-    v8::Isolate* isolate, v8::Handle<v8::Function> callback) {
-  return gin::CreateHandle(isolate, new WaitingCallback(isolate, callback));
+  Cancel();
 }
 
 // static
 void WaitingCallback::CallOnHandleReady(void* closure, MojoResult result) {
   static_cast<WaitingCallback*>(closure)->OnHandleReady(result);
 }
 
 void WaitingCallback::OnHandleReady(MojoResult result) {
   wait_id_ = 0;
 
   if (!runner_)
     return;
 
   gin::Runner::Scope scope(runner_.get());
   v8::Isolate* isolate = runner_->GetContextHolder()->isolate();
 
   v8::Handle<v8::Value> hidden_value =
       GetWrapper(isolate)->GetHiddenValue(GetHiddenPropertyName(isolate));
   v8::Handle<v8::Function> callback;
   CHECK(gin::ConvertFromV8(isolate, hidden_value, &callback));
 
   v8::Handle<v8::Value> args[] = { gin::ConvertToV8(isolate, result) };
   runner_->Call(callback, runner_->global(), 1, args);
 }
 
 }  // namespace js
 }  // namespace mojo