Fix crash when TTS utterances are queued on shutdown.

chrome/browser/extensions/extension_tts_engine_api.cc

 // 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.
 
 #include "chrome/browser/extensions/extension_tts_engine_api.h"
 
 #include <string>
 
 #include "base/json/json_writer.h"
 #include "base/values.h"
@@ skipping 62 matching lines @@
       result_voice->Set(constants::kEventTypesKey, event_types);
       result_voices->Append(result_voice);
     }
   }
 }
 
 bool GetMatchingExtensionVoice(
     Utterance* utterance,
     const Extension** matching_extension,
     size_t* voice_index) {
+  // This will only happen during unit testing. Otherwise, an utterance
+  // will always have an associated profile.
+  if (!utterance->profile())
+    return false;
+
   ExtensionService* service = utterance->profile()->GetExtensionService();
   DCHECK(service);
   ExtensionEventRouter* event_router =
       utterance->profile()->GetExtensionEventRouter();
   DCHECK(event_router);
 
   *matching_extension = NULL;
   *voice_index = -1;
   const ExtensionList* extensions = service->extensions();
   ExtensionList::const_iterator iter;
@@ skipping 159 matching lines @@
     std::string error_message;
     event->GetString(constants::kErrorMessageKey, &error_message);
     controller->OnTtsEvent(
         utterance_id, TTS_EVENT_ERROR, char_index, error_message);
   } else {
     EXTENSION_FUNCTION_VALIDATE(false);
   }
 
   return true;
 }