cc: Split Proxy to eliminate unnecessary dependencies on the impl side

cc/test/fake_impl_proxy.h

-// Copyright 2012 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_TEST_FAKE_IMPL_PROXY_H_
-#define CC_TEST_FAKE_IMPL_PROXY_H_
-
-#include "base/thread_task_runner_handle.h"
-#include "cc/test/fake_proxy.h"
-#include "cc/trees/single_thread_proxy.h"
-
-namespace base {
-class SingleThreadIdleTaskRunner;
-}
-
-namespace cc {
-
-class FakeImplProxy : public FakeProxy {
- public:
-  FakeImplProxy()
-      : FakeProxy(base::ThreadTaskRunnerHandle::Get(), nullptr),
-        set_impl_thread_(this) {}
-
-  explicit FakeImplProxy(
-      scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner)
-      : FakeProxy(base::ThreadTaskRunnerHandle::Get(), impl_task_runner),
-        set_impl_thread_(this) {}
-
- private:
-  DebugScopedSetImplThread set_impl_thread_;
-};
-
-}  // namespace cc
-
-#endif  // CC_TEST_FAKE_IMPL_PROXY_H_