Updates the mic icon status based on the device's audio state.

chrome/browser/ui/app_list/start_page_service.h

Index: chrome/browser/ui/app_list/start_page_service.h
diff --git a/chrome/browser/ui/app_list/start_page_service.h b/chrome/browser/ui/app_list/start_page_service.h
index 61e226055de48df5c1ac945ab210ba55c6aaf6d9..d33bd531bbd29826fc90f2c6560ed88b22da43ed 100644
--- a/chrome/browser/ui/app_list/start_page_service.h
+++ b/chrome/browser/ui/app_list/start_page_service.h
@@ -88,6 +88,12 @@ class StartPageService : public KeyedService,
   // getUserMedia() request from the web contents.
   class StartPageWebContentsDelegate;
 
+#if defined(OS_CHROMEOS)
+  // This class observes the change of audio input device availability and
+  // checks if currently the system has valid audio input.
+  class AudioStatus;
+#endif
+
   void LoadContents();
   void UnloadContents();
 
@@ -109,6 +115,10 @@ class StartPageService : public KeyedService,
 
   scoped_ptr<SpeechRecognizer> speech_recognizer_;
 
+#if defined(OS_CHROMEOS)
+  scoped_ptr<AudioStatus> audio_status_;
+#endif
+
   base::WeakPtrFactory<StartPageService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(StartPageService);