Remove WebKit::Platform dependencies from cc

cc/timer.h

-// Copyright 2011 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 CCTimer_h
-#define CCTimer_h
-
-namespace cc {
-
-class Thread;
-class TimerTask;
-
-class TimerClient {
-public:
-    virtual ~TimerClient() { }
-
-    virtual void onTimerFired() = 0;
-};
-
-class Timer {
-public:
-    Timer(Thread*, TimerClient*);
-    ~Timer();
-
-    // If a previous task is pending, it will be replaced with the new one.
-    void startOneShot(double intervalSeconds);
-    void stop();
-
-    bool isActive() const { return m_task; }
-
-private:
-    friend class TimerTask;
-
-    TimerClient* m_client;
-    Thread* m_thread;
-    TimerTask* m_task; // weak pointer
-};
-
-}  // namespace cc
-
-#endif