Support onvoiceschanged for extension-based tts engines.

chrome/browser/speech/extension_api/tts_extension_api.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/extension_api/tts_extension_api.h"
 
 #include <string>
 
 #include "base/lazy_instance.h"
 #include "base/memory/weak_ptr.h"
 #include "base/values.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/speech/extension_api/tts_engine_extension_api.h"
+#include "chrome/browser/speech/extension_api/tts_engine_extension_observer.h"
 #include "chrome/browser/speech/extension_api/tts_extension_api_constants.h"
 #include "chrome/browser/speech/tts_controller.h"
 #include "extensions/browser/event_router.h"
 #include "extensions/browser/extension_function_registry.h"
 #include "ui/base/l10n/l10n_util.h"
 
 namespace constants = tts_extension_api_constants;
 
 namespace events {
 const char kOnEvent[] = "tts.onEvent";
@@ skipping 319 matching lines @@
 TtsAPI::TtsAPI(content::BrowserContext* context) {
   ExtensionFunctionRegistry* registry =
       ExtensionFunctionRegistry::GetInstance();
   registry->RegisterFunction<ExtensionTtsEngineSendTtsEventFunction>();
   registry->RegisterFunction<TtsGetVoicesFunction>();
   registry->RegisterFunction<TtsIsSpeakingFunction>();
   registry->RegisterFunction<TtsSpeakFunction>();
   registry->RegisterFunction<TtsStopSpeakingFunction>();
   registry->RegisterFunction<TtsPauseFunction>();
   registry->RegisterFunction<TtsResumeFunction>();
+
+  // Ensure we're observing newly added engines for the given context.
+  TtsEngineExtensionObserver::GetInstance(Profile::FromBrowserContext(context));
 }
 
 TtsAPI::~TtsAPI() {
 }
 
 static base::LazyInstance<BrowserContextKeyedAPIFactory<TtsAPI> > g_factory =
     LAZY_INSTANCE_INITIALIZER;
 
 BrowserContextKeyedAPIFactory<TtsAPI>* TtsAPI::GetFactoryInstance() {
   return g_factory.Pointer();
 }
 
 }  // namespace extensions