Added a CallbackLayerAnimationObserver.

ui/compositor/test/layer_animation_observer_test_api.h

Index: ui/compositor/test/layer_animation_observer_test_api.h
diff --git a/ui/compositor/test/layer_animation_observer_test_api.h b/ui/compositor/test/layer_animation_observer_test_api.h
new file mode 100644
index 0000000000000000000000000000000000000000..35889b5b3879d73ce36b04faa686b0864246d222
--- /dev/null
+++ b/ui/compositor/test/layer_animation_observer_test_api.h
@@ -0,0 +1,34 @@
+// Copyright 2015 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_TEST_LAYER_ANIMATION_OBSERVER_TEST_API_H_
+#define UI_COMPOSITOR_TEST_LAYER_ANIMATION_OBSERVER_TEST_API_H_
+
+#include "base/macros.h"
+#include "ui/compositor/layer_animation_observer.h"
+
+namespace ui {
+namespace test {
+
+// Test API to provide internal access to the LayerAnimationObserver class.
+class LayerAnimationObserverTestApi {
+ public:
+  explicit LayerAnimationObserverTestApi(LayerAnimationObserver* observer);
+
+  // Wrappers for LayerAnimationObserver:

[danakj, 2015/10/12 21:33:56]

s/:/./

[bruthig, 2015/10/13 19:41:42]

I'm not 100% what you meant here, assuming you meant change the ':' to a '.'.

+  void AttachedToSequence(LayerAnimationSequence* sequence);
+  void DetachedFromSequence(LayerAnimationSequence* sequence,
+                            bool send_notification);
+
+ private:
+  // The instance to provide internal access to.
+  LayerAnimationObserver* observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(LayerAnimationObserverTestApi);
+};
+
+}  // namespace test
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_TEST_LAYER_ANIMATION_OBSERVER_TEST_API_H_