Uses a system-wide notion of isSpeaking in the Mac extension TTS api.

chrome/browser/speech/extension_api/tts_extension_api_chromeos.cc

Index: chrome/browser/speech/extension_api/tts_extension_api_chromeos.cc
diff --git a/chrome/browser/speech/extension_api/tts_extension_api_chromeos.cc b/chrome/browser/speech/extension_api/tts_extension_api_chromeos.cc
index 45d82202449c548564a06aa1b69c3b2616428583..08a31d18d0d6491e4731600ed7fa474533298595 100644
--- a/chrome/browser/speech/extension_api/tts_extension_api_chromeos.cc
+++ b/chrome/browser/speech/extension_api/tts_extension_api_chromeos.cc
@@ -47,6 +47,8 @@ class ExtensionTtsPlatformImplChromeOs
 
   virtual bool StopSpeaking();
 
+  virtual bool IsSpeaking();
+
   virtual bool SendsEvent(TtsEventType event_type);
 
   // Get the single instance of this class.
@@ -163,6 +165,11 @@ bool ExtensionTtsPlatformImplChromeOs::StopSpeaking() {
   return true;
 }
 
+bool ExtensionTtsPlatformImplChromeOs::IsSpeaking() {
+  // Defers to controller's utterance based detection of is speaking.
+  return true;
+}
+
 bool ExtensionTtsPlatformImplChromeOs::SendsEvent(TtsEventType event_type) {
   return (event_type == TTS_EVENT_START ||
           event_type == TTS_EVENT_END ||