Remove parts of //cc we aren't using

cc/debug/unittest_only_benchmark_impl.h

-// Copyright 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_DEBUG_UNITTEST_ONLY_BENCHMARK_IMPL_H_
-#define CC_DEBUG_UNITTEST_ONLY_BENCHMARK_IMPL_H_
-
-#include "base/memory/weak_ptr.h"
-#include "cc/debug/micro_benchmark_impl.h"
-
-namespace base {
-class Value;
-class MessageLoopProxy;
-}
-
-namespace cc {
-
-class LayerTreeHostImpl;
-class CC_EXPORT UnittestOnlyBenchmarkImpl : public MicroBenchmarkImpl {
- public:
-  UnittestOnlyBenchmarkImpl(scoped_refptr<base::MessageLoopProxy> origin_loop,
-                            base::Value* settings,
-                            const DoneCallback& callback);
-  ~UnittestOnlyBenchmarkImpl() override;
-
-  void DidCompleteCommit(LayerTreeHostImpl* host) override;
-};
-
-}  // namespace cc
-
-#endif  // CC_DEBUG_UNITTEST_ONLY_BENCHMARK_IMPL_H_