compositor: Tick the UI animations from cc, instead of from timer callbacks.

ui/compositor/layer_animator_collection.h

Index: ui/compositor/layer_animator_collection.h
diff --git a/ui/compositor/layer_animator_collection.h b/ui/compositor/layer_animator_collection.h
new file mode 100644
index 0000000000000000000000000000000000000000..d535c48e2bcb3e3b7d30d12ecce7781798ac6259
--- /dev/null
+++ b/ui/compositor/layer_animator_collection.h
@@ -0,0 +1,54 @@
+// 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_COMPOSITOR_LAYER_ANIMATOR_COLLECTION_H_
+#define UI_COMPOSITOR_LAYER_ANIMATOR_COLLECTION_H_
+
+#include <set>
+
+#include "base/callback.h"
+#include "base/lazy_instance.h"
+#include "base/memory/ref_counted.h"
+#include "base/time/time.h"
+#include "ui/compositor/compositor_export.h"
+
+namespace base {
+class TimeTicks;
+}
+
+namespace ui {
+
+class LayerAnimator;
+
+// A collection of LayerAnimators that should be updated at each animation step
+// in the compositor.
+class COMPOSITOR_EXPORT LayerAnimatorCollection {
+ public:
+  static LayerAnimatorCollection* GetInstance();
+
+  void StartAnimator(scoped_refptr<LayerAnimator> animator);
+  void StopAnimator(scoped_refptr<LayerAnimator> animator);
+
+  bool HasActiveAnimators() const;
+
+  void Progress(base::TimeTicks now);
+
+  base::TimeTicks last_tick_time() const { return last_tick_time_; }
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<LayerAnimatorCollection>;
+
+  LayerAnimatorCollection();
+  ~LayerAnimatorCollection();
+
+  base::TimeTicks last_tick_time_;
+
+  std::set<scoped_refptr<LayerAnimator> > animators_;
+
+  DISALLOW_COPY_AND_ASSIGN(LayerAnimatorCollection);
+};
+
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_LAYER_ANIMATOR_COLLECTION_H_