chrome: Cleanup class/struct forward declarations

chrome/browser/speech/extension_api/tts_engine_extension_api.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 CHROME_BROWSER_SPEECH_EXTENSION_API_TTS_ENGINE_EXTENSION_API_H_
 #define CHROME_BROWSER_SPEECH_EXTENSION_API_TTS_ENGINE_EXTENSION_API_H_
 
 #include <vector>
 
 #include "base/memory/singleton.h"
 #include "chrome/browser/speech/tts_controller.h"
 #include "extensions/browser/extension_function.h"
 
 class Utterance;
 
-namespace base {
-class ListValue;
-}
-
 namespace content {
 class BrowserContext;
 }
 
-namespace extensions {
-class Extension;
-}
-
 namespace tts_engine_events {
 extern const char kOnSpeak[];
 extern const char kOnStop[];
 extern const char kOnPause[];
 extern const char kOnResume[];
 }
 
 // TtsEngineDelegate implementation used by TtsController.
 class TtsExtensionEngine : public TtsEngineDelegate {
  public:
@@ skipping 13 matching lines @@
 // to send events back to the client that's calling tts.speak().
 class ExtensionTtsEngineSendTtsEventFunction
     : public UIThreadExtensionFunction {
  private:
   ~ExtensionTtsEngineSendTtsEventFunction() override {}
   ResponseAction Run() override;
   DECLARE_EXTENSION_FUNCTION("ttsEngine.sendTtsEvent", TTSENGINE_SENDTTSEVENT)
 };
 
 #endif  // CHROME_BROWSER_SPEECH_EXTENSION_API_TTS_ENGINE_EXTENSION_API_H_