Thread ui opacity animations

cc/animation_id_provider.h

Index: cc/animation_id_provider.h
diff --git a/cc/animation_id_provider.h b/cc/animation_id_provider.h
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+++ b/cc/animation_id_provider.h
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+// Copyright (c) 2013 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 CC_ANIMATION_ID_PROVIDER
+#define CC_ANIMATION_ID_PROVIDER
+
+#include "cc/cc_export.h"
+
+namespace cc {
+
+class CC_EXPORT AnimationIdProvider {
+ public:
+  // These functions each return monotonically increasing values.
+  static int NextAnimationId();
+  static int NextGroupId();
+};
+
+}
+
+#endif  // CC_ANIMATION_ID_PROVIDER