NOT READY FOR REVIEW - Add support for custom animation timers.

ui/compositor/layer_animation_timer.h

Index: ui/compositor/layer_animation_timer.h
diff --git a/ui/compositor/layer_animation_timer.h b/ui/compositor/layer_animation_timer.h
new file mode 100644
index 0000000000000000000000000000000000000000..9a6dfb8b6e4e16283a6b03d35fa49c30ba4caf0d
--- /dev/null
+++ b/ui/compositor/layer_animation_timer.h
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+// Copyright (c) 2012 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_COMPOSITOR_LAYER_ANIMATION_TIMER_H_
+#define UI_COMPOSITOR_LAYER_ANIMATION_TIMER_H_
+
+#include "ui/base/animation/animation_container.h"
+#include "ui/compositor/compositor_export.h"
+
+namespace ui {
+
+class COMPOSITOR_EXPORT LayerAnimationTimer {
+ public:
+  virtual ~LayerAnimationTimer() {
+  }
+
+  virtual void Start(AnimationContainerElement*) = 0;
+  virtual void Stop(AnimationContainerElement*) = 0;
+  virtual base::TimeTicks last_tick_time() const = 0;
+  virtual bool is_running() const = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_LAYER_ANIMATION_TIMER_H_