Support onvoiceschanged for extension-based tts engines.

chrome/browser/speech/tts_chromeos.cc

 // 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.
 
-#include "chrome/browser/speech/tts_extension_loader_chromeos.h"
+#include "chrome/browser/extensions/component_loader.h"
+#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/speech/tts_engine_extension_observer.h"
 #include "chrome/browser/speech/tts_platform.h"
+#include "chrome/common/extensions/extension_constants.h"
+#include "extensions/browser/extension_system.h"
 
 // Chrome OS doesn't have native TTS, instead it includes a built-in
 // component extension that provides speech synthesis. This class includes
 // an implementation of LoadBuiltInTtsExtension and dummy implementations of
 // everything else.
 class TtsPlatformImplChromeOs
     : public TtsPlatformImpl {
  public:
   // TtsPlatformImpl overrides:
   virtual bool PlatformImplAvailable() OVERRIDE {
     return false;
   }
 
   virtual bool LoadBuiltInTtsExtension(Profile* profile) OVERRIDE {
-    return TtsExtensionLoaderChromeOs::GetInstance(profile)->LoadTtsExtension();
+    // Check to see if the engine was previously loaded.
+    if (TtsEngineExtensionObserver::GetInstance(profile)->SawExtensionLoad(
+            extension_misc::kSpeechSynthesisExtensionId, true)) {
+      return false;
+    }
+
+    // Load the component extension into this profile.
+    ExtensionService* extension_service =
+        extensions::ExtensionSystem::Get(profile)->extension_service();
+    DCHECK(extension_service);
+    extension_service->component_loader()
+        ->AddChromeOsSpeechSynthesisExtension();
+    return true;
   }
 
   virtual bool Speak(
       int utterance_id,
       const std::string& utterance,
       const std::string& lang,
       const VoiceData& voice,
       const UtteranceContinuousParameters& params) OVERRIDE {
     return false;
   }
@@ skipping 28 matching lines @@
 // static
 TtsPlatformImpl* TtsPlatformImpl::GetInstance() {
   return TtsPlatformImplChromeOs::GetInstance();
 }
 
 // static
 TtsPlatformImplChromeOs*
 TtsPlatformImplChromeOs::GetInstance() {
   return Singleton<TtsPlatformImplChromeOs>::get();
 }