[Hotword] Delay checking for audio devices until needed.

chrome/browser/search/hotword_service_factory.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SEARCH_HOTWORD_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_SEARCH_HOTWORD_SERVICE_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "chrome/browser/media/media_capture_devices_dispatcher.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
@@ skipping 17 matching lines @@
   static bool IsHotwordAllowed(content::BrowserContext* context);
 
   // Returns the current error message for the service for |context|.
   // A value of 0 indicates no error.
   static int GetCurrentError(content::BrowserContext* context);
 
   // Returns the current known state of the microphone. Since this state
   // 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
   void OnUpdateAudioDevices(
       const content::MediaStreamDevices& devices) override;
 
   // This will kick off the monitor that calls OnUpdateAudioDevices when the
   // number of audio devices changes (or is initialized). It needs to be a
   // separate function so it can be called after the service is initialized
   // (i.e., after startup). The monitor can't be initialized during startup
   // because it would slow down startup too much so it is delayed and not
   // called until it's needed by the webui in browser_options_handler.
@@ skipping 12 matching lines @@
       content::BrowserContext* context) const override;
 
   // Must be called from the UI thread since the instance of
   // MediaCaptureDevicesDispatcher can only be accessed on the UI thread.
   void InitializeMicrophoneObserver();
 
   bool microphone_available() { return microphone_available_; }
 
   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);
 };
 
 #endif  // CHROME_BROWSER_SEARCH_HOTWORD_SERVICE_FACTORY_H_