Remove parts of //cc we aren't using

cc/animation/animation_id_provider.cc

-// 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.
-
-#include "base/atomic_sequence_num.h"
-#include "cc/animation/animation_id_provider.h"
-
-namespace cc {
-
-base::StaticAtomicSequenceNumber g_next_animation_id;
-base::StaticAtomicSequenceNumber g_next_group_id;
-
-int AnimationIdProvider::NextAnimationId() {
-  // Animation IDs start from 1.
-  return g_next_animation_id.GetNext() + 1;
-}
-
-int AnimationIdProvider::NextGroupId() {
-  // Animation group IDs start from 1.
-  return g_next_group_id.GetNext() + 1;
-}
-
-}  // namespace cc