speech: Change SpeechInputBubbleBase::message_text() to return a const-ref.

chrome/browser/speech/speech_input_bubble.h

 // Copyright (c) 2011 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_SPEECH_INPUT_BUBBLE_H_
 #define CHROME_BROWSER_SPEECH_SPEECH_INPUT_BUBBLE_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 134 matching lines @@
   virtual void SetInputVolume(float volume, float noise_volume) OVERRIDE;
   virtual content::WebContents* web_contents() OVERRIDE;
 
  protected:
   // Updates the platform specific UI layout for the current display mode.
   virtual void UpdateLayout() = 0;
 
   // Overridden by subclasses to copy |icon_image()| to the screen.
   virtual void UpdateImage() = 0;
 
-  DisplayMode display_mode() {
-    return display_mode_;
-  }
+  DisplayMode display_mode() const { return display_mode_; }
 
-  string16 message_text() {
-    return message_text_;
-  }
+  const string16& message_text() const { return message_text_; }
 
   SkBitmap icon_image();
 
  private:
   void DoRecognizingAnimationStep();
   void DoWarmingUpAnimationStep();
   void SetImage(const SkBitmap& image);
 
   void DrawVolumeOverlay(SkCanvas* canvas,
                          const SkBitmap& bitmap,
@@ skipping 17 matching lines @@
   scoped_ptr<SkBitmap> icon_image_;
 };
 
 // This typedef is to workaround the issue with certain versions of
 // Visual Studio where it gets confused between multiple Delegate
 // classes and gives a C2500 error. (I saw this error on the try bots -
 // the workaround was not needed for my machine).
 typedef SpeechInputBubble::Delegate SpeechInputBubbleDelegate;
 
 #endif  // CHROME_BROWSER_SPEECH_SPEECH_INPUT_BUBBLE_H_