cc: Add UniqueNotifier to cc/base.

cc/base/unique_notifier.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 "cc/base/unique_notifier.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/location.h"
+#include "base/sequenced_task_runner.h"
+
+namespace cc {
+
+UniqueNotifier::UniqueNotifier(base::SequencedTaskRunner* task_runner,
+                               const base::Closure& closure)
+    : task_runner_(task_runner),
+      closure_(closure),
+      notification_pending_(false),
+      weak_ptr_factory_(this) {
+}
+
+UniqueNotifier::~UniqueNotifier() {
+}
+
+void UniqueNotifier::Schedule() {
+  if (notification_pending_)
+    return;
+
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&UniqueNotifier::Notify, weak_ptr_factory_.GetWeakPtr()));
+  notification_pending_ = true;
+}
+
+void UniqueNotifier::Notify() {
+  // Note that the order here is important in case closure schedules another
+  // run.
+  notification_pending_ = false;
+  closure_.Run();
+}
+
+}  // namespace cc