Mojo: Cancel WaitingCallbacks when their HandleWrappers are closed.

mojo/bindings/js/waiting_callback.h

 // 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.
 
 #ifndef MOJO_BINDINGS_JS_WAITING_CALLBACK_H_
 #define MOJO_BINDINGS_JS_WAITING_CALLBACK_H_
 
 #include "gin/handle.h"
 #include "gin/runner.h"
 #include "gin/wrappable.h"
+#include "mojo/bindings/js/handle.h"
+#include "mojo/bindings/js/handle_close_observer.h"
 #include "mojo/public/c/environment/async_waiter.h"
 #include "mojo/public/cpp/system/core.h"
 
 namespace mojo {
 namespace js {
 
-class WaitingCallback : public gin::Wrappable<WaitingCallback> {
+class WaitingCallback : public gin::Wrappable<WaitingCallback>,
+                        public gin::HandleCloseObserver {
  public:
   static gin::WrapperInfo kWrapperInfo;
 
   // Creates a new WaitingCallback.
   static gin::Handle<WaitingCallback> Create(
       v8::Isolate* isolate,
       v8::Handle<v8::Function> callback,
-      mojo::Handle handle,
+      gin::Handle<gin::HandleWrapper> handle_wrapper,
       MojoHandleSignals signals);
 
   // Cancels the callback. Does nothing if a callback is not pending. This is
   // implicitly invoked from the destructor but can be explicitly invoked as
   // necessary.
   void Cancel();
 
  private:
-  WaitingCallback(v8::Isolate* isolate, v8::Handle<v8::Function> callback);
+  WaitingCallback(v8::Isolate* isolate,
+                  v8::Handle<v8::Function> callback,
+                  gin::Handle<gin::HandleWrapper> handle_wrapper);
   virtual ~WaitingCallback();
 
   // Callback from MojoAsyncWaiter. |closure| is the WaitingCallback.
   static void CallOnHandleReady(void* closure, MojoResult result);
 
   // Invoked from CallOnHandleReady() (CallOnHandleReady() must be static).
   void OnHandleReady(MojoResult result);
 
+  // Invoked by the HandleWrapper if the handle is closed while this wait is
+  // still in progress.
+  virtual void OnWillCloseHandle() OVERRIDE;
+
   base::WeakPtr<gin::Runner> runner_;
   MojoAsyncWaitID wait_id_;
 
+  gin::HandleWrapper* handle_wrapper_;
+
   DISALLOW_COPY_AND_ASSIGN(WaitingCallback);
 };
 
 }  // namespace js
 }  // namespace mojo
 
 #endif  // MOJO_BINDINGS_JS_WAITING_CALLBACK_H_