Fix crash when TTS utterances are queued on shutdown.

chrome/browser/extensions/extension_tts_api_controller.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_EXTENSIONS_EXTENSION_TTS_API_CONTROLLER_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_TTS_API_CONTROLLER_H_
 
 #include <queue>
 #include <set>
 #include <string>
@@ skipping 201 matching lines @@
                   const std::string& error_message);
 
   // Return a list of all available voices, including the native voice,
   // if supported, and all voices registered by extensions.
   base::ListValue* GetVoices(Profile* profile);
 
   // For unit testing.
   void SetPlatformImpl(ExtensionTtsPlatformImpl* platform_impl);
   int QueueSize();
 
- private:
+ protected:
   ExtensionTtsController();
   virtual ~ExtensionTtsController();
 
+ private:
   // Get the platform TTS implementation (or injected mock).
   ExtensionTtsPlatformImpl* GetPlatformImpl();
 
   // Start speaking the given utterance. Will either take ownership of
   // |utterance| or delete it if there's an error. Returns true on success.
   void SpeakNow(Utterance* utterance);
 
-  // Clear the utterance queue.
-  void ClearUtteranceQueue();
+  // Clear the utterance queue. If send_events is true, will send
+  // TTS_EVENT_CANCELLED events on each one.
+  void ClearUtteranceQueue(bool send_events);
 
   // Finalize and delete the current utterance.
   void FinishCurrentUtterance();
 
   // Start speaking the next utterance in the queue.
   void SpeakNextUtterance();
 
   friend struct DefaultSingletonTraits<ExtensionTtsController>;
 
   // The current utterance being spoken.
   Utterance* current_utterance_;
 
   // A queue of utterances to speak after the current one finishes.
   std::queue<Utterance*> utterance_queue_;
 
   // A pointer to the platform implementation of text-to-speech, for
   // dependency injection.
   ExtensionTtsPlatformImpl* platform_impl_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionTtsController);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_TTS_API_CONTROLLER_H_