Delete unused code in chrome/common or mark them as platform specific.

chrome/common/tts_utterance_request.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 "chrome/common/tts_utterance_request.h"
 
 TtsUtteranceRequest::TtsUtteranceRequest()
     : id(0),
       volume(1.0),
       rate(1.0),
       pitch(1.0) {
 }
 
 TtsUtteranceRequest::~TtsUtteranceRequest() {
 }
 
 TtsVoice::TtsVoice()
     : local_service(true),
       is_default(false) {
 }
 
 TtsVoice::~TtsVoice() {
 }
-
-TtsUtteranceResponse::TtsUtteranceResponse()
-    : id(0) {
-}
-
-TtsUtteranceResponse::~TtsUtteranceResponse() {
-}