Added a CallbackLayerAnimationObserver.

ui/compositor/test/layer_animation_observer_test_api.cc

+// 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.
+
+#include "ui/compositor/test/layer_animation_observer_test_api.h"
+
+namespace ui {
+namespace test {
+
+LayerAnimationObserverTestApi::LayerAnimationObserverTestApi(
+    LayerAnimationObserver* observer)
+    : observer_(observer) {}
+
+void LayerAnimationObserverTestApi::AttachedToSequence(
+    LayerAnimationSequence* sequence) {
+  observer_->AttachedToSequence(sequence);
+}
+
+void LayerAnimationObserverTestApi::DetachedFromSequence(
+    LayerAnimationSequence* sequence,
+    bool send_notification) {
+  observer_->DetachedFromSequence(sequence, send_notification);
+}
+
+}  // namespace test
+}  // namespace ui