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

chrome/browser/ui/app_list/start_page_service.cc

Index: chrome/browser/ui/app_list/start_page_service.cc
diff --git a/chrome/browser/ui/app_list/start_page_service.cc b/chrome/browser/ui/app_list/start_page_service.cc
index 930088926bb181fb02b5843816e4977750cc15e6..b9216b75751ef55fa1576a76302c702a20e1ee49 100644
--- a/chrome/browser/ui/app_list/start_page_service.cc
+++ b/chrome/browser/ui/app_list/start_page_service.cc
@@ -36,6 +36,10 @@
 #include "extensions/common/extension.h"
 #include "ui/app_list/app_list_switches.h"
 
+#if defined(OS_CHROMEOS)
+#include "chromeos/audio/cras_audio_handler.h"
+#endif
+
 using base::RecordAction;
 using base::UserMetricsAction;
 
@@ -48,7 +52,7 @@ bool InSpeechRecognition(SpeechRecognitionState state) {
       state == SPEECH_RECOGNITION_IN_SPEECH;
 }
 
-}
+}  // namespace
 
 class StartPageService::ProfileDestroyObserver
     : public content::NotificationObserver {
@@ -102,6 +106,48 @@ class StartPageService::StartPageWebContentsDelegate
   DISALLOW_COPY_AND_ASSIGN(StartPageWebContentsDelegate);
 };
 
+#if defined(OS_CHROMEOS)
+
+class StartPageService::AudioStatus
+    : public chromeos::CrasAudioHandler::AudioObserver {
+ public:
+  explicit AudioStatus(StartPageService* start_page_service)
+      : start_page_service_(start_page_service) {
+    chromeos::CrasAudioHandler::Get()->AddAudioObserver(this);
+    CheckAndUpdate();
+  }
+
+  ~AudioStatus() override {
+    chromeos::CrasAudioHandler::Get()->RemoveAudioObserver(this);
+  }
+
+  bool CanListen() {
+    chromeos::CrasAudioHandler* audio_handler =
+        chromeos::CrasAudioHandler::Get();
+    return (audio_handler->GetPrimaryActiveInputNode() != 0) &&
+           !audio_handler->IsInputMuted();
+  }
+
+ private:
+  void CheckAndUpdate() {
+    // TODO(mukai): If the system can listen, this should also restart the
+    // hotword recognition.
+    start_page_service_->OnSpeechRecognitionStateChanged(
+        CanListen() ? SPEECH_RECOGNITION_READY : SPEECH_RECOGNITION_OFF);
+  }
+
+  // chromeos::CrasAudioHandler::AudioObserver:
+  void OnInputMuteChanged() override { CheckAndUpdate(); }
+
+  void OnActiveInputNodeChanged() override { CheckAndUpdate(); }
+
+  StartPageService* start_page_service_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioStatus);
+};
+
+#endif  // OS_CHROMEOS
+
 // static
 StartPageService* StartPageService::Get(Profile* profile) {
   return StartPageServiceFactory::GetForProfile(profile);
@@ -119,8 +165,9 @@ StartPageService::StartPageService(Profile* profile)
   // If experimental hotwording is enabled, then we're always "ready".
   // Transitioning into the "hotword recognizing" state is handled by the
   // hotword extension.
-  if (HotwordService::IsExperimentalHotwordingEnabled())
+  if (HotwordService::IsExperimentalHotwordingEnabled()) {
     state_ = app_list::SPEECH_RECOGNITION_READY;
+  }
 
   if (app_list::switches::IsExperimentalAppListEnabled())
     LoadContents();
@@ -148,6 +195,10 @@ void StartPageService::AppListShown() {
         "appList.startPage.onAppListShown",
         base::FundamentalValue(HotwordEnabled()));
   }
+
+#if defined(OS_CHROMEOS)
+  audio_status_.reset(new AudioStatus(this));
+#endif
 }
 
 void StartPageService::AppListHidden() {
@@ -162,6 +213,10 @@ void StartPageService::AppListHidden() {
       speech_recognizer_) {
     speech_recognizer_->Stop();
   }
+
+#if defined(OS_CHROMEOS)
+  audio_status_.reset();
+#endif
 }
 
 void StartPageService::ToggleSpeechRecognition() {
@@ -251,6 +306,14 @@ void StartPageService::OnSpeechSoundLevelChanged(int16_t level) {
 
 void StartPageService::OnSpeechRecognitionStateChanged(
     SpeechRecognitionState new_state) {
+#if defined(OS_CHROMEOS)
+  // Sometimes this can be called even though there are no audio input devices.
+  if (!audio_status_->CanListen())
+    new_state = SPEECH_RECOGNITION_OFF;
+#endif
+
+  if (state_ == new_state)
+    return;
 
   if (HotwordService::IsExperimentalHotwordingEnabled() &&
       new_state == SPEECH_RECOGNITION_READY &&
@@ -283,6 +346,9 @@ content::WebContents* StartPageService::GetSpeechContents() {
 
 void StartPageService::Shutdown() {
   UnloadContents();
+#if defined(OS_CHROMEOS)
+  audio_status_.reset();
+#endif
 }
 
 void StartPageService::WebUILoaded() {