[mojo-bindings] Use Watcher API for JS bindings

mojo/edk/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/edk/js/waiting_callback.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "gin/per_context_data.h"
 
@@ skipping 10 matching lines @@
 
 }  // namespace
 
 gin::WrapperInfo WaitingCallback::kWrapperInfo = { gin::kEmbedderNativeGin };
 
 // static
 gin::Handle<WaitingCallback> WaitingCallback::Create(
     v8::Isolate* isolate,
     v8::Handle<v8::Function> callback,
     gin::Handle<HandleWrapper> handle_wrapper,
-    MojoHandleSignals signals) {
+    MojoHandleSignals signals,
+    bool one_shot) {
   gin::Handle<WaitingCallback> waiting_callback = gin::CreateHandle(
-      isolate, new WaitingCallback(isolate, callback, handle_wrapper));
-
-  waiting_callback->handle_watcher_.Start(
-      handle_wrapper->get(), signals, MOJO_DEADLINE_INDEFINITE,
+      isolate, new WaitingCallback(isolate, callback, one_shot));
+  waiting_callback->watcher_.Start(
+      handle_wrapper->get(), signals,
       base::Bind(&WaitingCallback::OnHandleReady,
                  base::Unretained(waiting_callback.get())));
   return waiting_callback;
 }
 
 void WaitingCallback::Cancel() {
-  if (!handle_watcher_.is_watching())
+  if (!watcher_.IsWatching())
     return;
 
-  RemoveHandleCloseObserver();
-  handle_watcher_.Stop();
+  watcher_.Cancel();
 }
 
 WaitingCallback::WaitingCallback(v8::Isolate* isolate,
                                  v8::Handle<v8::Function> callback,
-                                 gin::Handle<HandleWrapper> handle_wrapper)
-    : handle_wrapper_(handle_wrapper.get()),
+                                 bool one_shot)
+    : one_shot_(one_shot),
       weak_factory_(this) {
-  handle_wrapper_->AddCloseObserver(this);
   v8::Handle<v8::Context> context = isolate->GetCurrentContext();
   runner_ = gin::PerContextData::From(context)->runner()->GetWeakPtr();
   GetWrapper(isolate)
       ->SetPrivate(context, GetHiddenPropertyName(isolate), callback)
       .FromJust();
 }
 
 WaitingCallback::~WaitingCallback() {
   Cancel();
 }
 
-void WaitingCallback::RemoveHandleCloseObserver() {
-  handle_wrapper_->RemoveCloseObserver(this);
-  handle_wrapper_ = nullptr;
-}
-
 void WaitingCallback::OnHandleReady(MojoResult result) {

[yzshen1, 2016/03/08 23:02:42]

Nit: this method could be removed, because it only forwards to CallCallback().

-  RemoveHandleCloseObserver();
   CallCallback(result);
 }
 
 void WaitingCallback::CallCallback(MojoResult result) {
-  DCHECK(!handle_watcher_.is_watching());
-  DCHECK(!handle_wrapper_);
-
   if (!runner_)
     return;
 
+  DCHECK(watcher_.IsWatching() || result == MOJO_RESULT_CANCELLED);
+
   gin::Runner::Scope scope(runner_.get());
   v8::Isolate* isolate = runner_->GetContextHolder()->isolate();
 
   v8::Handle<v8::Value> hidden_value =
       GetWrapper(isolate)
           ->GetPrivate(runner_->GetContextHolder()->context(),
                        GetHiddenPropertyName(isolate))
           .ToLocalChecked();
   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);
-}
 
-void WaitingCallback::OnWillCloseHandle() {
-  handle_watcher_.Stop();
-
-  // This may be called from GC, so we can't execute Javascript now, call
-  // RemoveHandleCloseObserver explicitly, and CallCallback asynchronously.
-  RemoveHandleCloseObserver();
-  base::MessageLoop::current()->PostTask(
-      FROM_HERE,
-      base::Bind(&WaitingCallback::CallCallback, weak_factory_.GetWeakPtr(),
-                 MOJO_RESULT_INVALID_ARGUMENT));
+  if (one_shot_) {
+    runner_.reset();
+    Cancel();
+  }
 }
 
 }  // namespace js
 }  // namespace edk
 }  // namespace mojo