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..d4190201b10804ef3bd5bf431b074fa6f29daad0 100644
--- a/chrome/browser/ui/app_list/start_page_service.h
+++ b/chrome/browser/ui/app_list/start_page_service.h
@@ -20,6 +20,10 @@
 #include "content/public/browser/web_contents.h"
 #include "ui/app_list/speech_ui_model_observer.h"
 
+#if defined(OS_CHROMEOS)
+#include "chromeos/audio/cras_audio_handler.h"
+#endif
+
 namespace extensions {
 class Extension;
 }
@@ -35,7 +39,11 @@ class StartPageObserver;
 // StartPageService collects data to be displayed in app list's start page
 // and hosts the start page contents.
 class StartPageService : public KeyedService,
-                         public SpeechRecognizerDelegate {
+                         public SpeechRecognizerDelegate,

[tapted, 2014/11/25 05:03:11]

does this trailing comma break things?

I'm not really a fan of guarding parent classes with #ifdef - the code gets
unmaintainable quite quickly. Getting my head around all the speech-recognition
states is already quite hard.

It actually would't be too hard to subclass StartPageService with a
StartPageServiceChromeOS and just #ifdef around `new StartPageService(..)` and a
#include in start_page_service_factory.cc -- Can we do that?

Then make StartPageService::AppListShown virtual, or have AppListShown call
OnAppListShown at the end.


StartPageService::Create(Profile*) is another option. Then in
start_page_service.cc you would just need 

#if !defined(OS_CHROMEOS)
StartPageService* StartPageService::Create(Profile* profile) {
  return new StartPageService(profile);
}
#endif


with StartPageServiceChromeOS being provided in start_page_service_chromeos.cc

[Jun Mukai, 2014/11/26 01:39:21]

You are right.
I think StartPageServiceChromeOS is an overkill in this situation -- I factored
out the audio handling code into an internal class, named AudioDeviceStatus. 
WDYT?

[tapted, 2014/11/26 02:05:58]

looks good!

+#if defined(OS_CHROMEOS)
+                         public chromeos::CrasAudioHandler::AudioObserver
+#endif
+                         {
  public:
   typedef std::vector<scoped_refptr<const extensions::Extension> >
       ExtensionList;
@@ -94,6 +102,12 @@ class StartPageService : public KeyedService,
   // KeyedService overrides:
   void Shutdown() override;
 
+#if defined(OS_CHROMEOS)
+  // chromeos::CrasAudioHandler::AudioObserver:
+  void OnInputMuteChanged() override;
+  void OnActiveInputNodeChanged() override;
+#endif
+
   Profile* profile_;
   scoped_ptr<content::WebContents> contents_;
   scoped_ptr<StartPageWebContentsDelegate> contents_delegate_;