device: Cleanup class/struct forward declarations

device/gamepad/gamepad_test_helpers.h

 // Copyright (c) 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 DEVICE_GAMEPAD_GAMEPAD_TEST_HELPERS_H_
 #define DEVICE_GAMEPAD_GAMEPAD_TEST_HELPERS_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event.h"
 #include "device/gamepad/gamepad_data_fetcher.h"
 #include "device/gamepad/gamepad_shared_buffer.h"
 #include "third_party/WebKit/public/platform/WebGamepads.h"
 
 namespace device {
 
-class GamepadService;
-
 // Data fetcher that returns canned data for the gamepad provider.
 class MockGamepadDataFetcher : public GamepadDataFetcher {
  public:
   // Initializes the fetcher with the given gamepad data, which will be
   // returned when the provider queries us.
   explicit MockGamepadDataFetcher(const blink::WebGamepads& test_data);
 
   ~MockGamepadDataFetcher() override;
 
   GamepadSource source() override;
@@ skipping 48 matching lines @@
  private:
   // This must be constructed before the system monitor.
   base::MessageLoop message_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(GamepadTestHelper);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_GAMEPAD_GAMEPAD_TEST_HELPERS_H_