[Hotword] Delay checking for audio devices until needed.

chrome/browser/search/hotword_service_factory.h

Index: chrome/browser/search/hotword_service_factory.h
diff --git a/chrome/browser/search/hotword_service_factory.h b/chrome/browser/search/hotword_service_factory.h
index c07b6510819f0ea80dac27a8e23a048a786611a3..cc26b48180afd8dcde6afe137354267934a64f9f 100644
--- a/chrome/browser/search/hotword_service_factory.h
+++ b/chrome/browser/search/hotword_service_factory.h
@@ -35,6 +35,11 @@ class HotwordServiceFactory : public MediaCaptureDevicesDispatcher::Observer,
   // is browser (not profile) specific, it resides in the factory.
   static bool IsMicrophoneAvailable();
 
+  // Returns whether the state of the audio devices has been updated.
+  // Essentially it indicates the validity of the return value from
+  // IsMicrophoneAvailable().
+  static bool IsAudioDeviceStateUpdated();
+
   // Overridden from MediaCaptureDevicesDispatcher::Observer
   virtual void OnUpdateAudioDevices(
       const content::MediaStreamDevices& devices) override;
@@ -67,6 +72,13 @@ class HotwordServiceFactory : public MediaCaptureDevicesDispatcher::Observer,
 
   bool microphone_available_;
 
+  // Indicates if the check for audio devices has been run such that it can be
+  // included in the error checking. Audio checking is not done immediately
+  // upon start up because of the negative impact on performance.
+  bool audio_device_state_updated_;
+
+  bool audio_device_state_updated() { return audio_device_state_updated_; }
+
   DISALLOW_COPY_AND_ASSIGN(HotwordServiceFactory);
 };