Unified BeginFrame scheduling

ui/base/compositor/begin_frame_manager.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 UI_BASE_COMPOSITOR_BEGIN_FRAME_MANAGER_H_
+#define UI_BASE_COMPOSITOR_BEGIN_FRAME_MANAGER_H_
+
+#include "base/basictypes.h"
+#include "base/observer_list.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/time/time.h"
+#include "ui/base/ui_base_export.h"
+
+namespace cc {
+struct BeginFrameArgs;
+}
+
+namespace ui {
+
+// This class delivers a BeginFrame request from the Compositor to its
+// observers. It also handles next BeginFrame scheduling via its delegate.
+// Browser compositor will own this.
+// This class will be run only on main thread.
+class UI_BASE_EXPORT BeginFrameManager : public base::NonThreadSafe {
+ public:
+  // Subclass should deliver BeginFrame to its client.
+  class Observer {
+   public:
+    virtual void OnSendBeginFrame(const cc::BeginFrameArgs& args) = 0;
+  };
+
+  // Subclass should implement howto schedule next BeginFrame.
+  class Delegate {
+   public:
+    virtual void RequestBeginFrame() = 0;
+  };
+
+  BeginFrameManager(Delegate* delegate);
+  ~BeginFrameManager();
+
+  void SendBeginFrame(const cc::BeginFrameArgs& args);
+  void RequestBeginFrame() const;
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+ private:
+  // Not owned by this class.
+  Delegate* delegate_;
+  ObserverList<BeginFrameManager::Observer> observer_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(BeginFrameManager);
+};
+
+}  // namespace ui
+
+#endif  // UI_BASE_COMPOSITOR_BEGIN_FRAME_MANAGER_H_