Implement HasInputDevices in CrasAudioManager

chromeos/audio/cras_audio_handler.h

 // Copyright (c) 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 CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_
 #define CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_
 
 #include <stdint.h>
 #include <queue>
 
@@ skipping 110 matching lines @@
   // Gets volume level in 0-100% range (0 being pure silence) for a device.
   virtual int GetInputGainPercentForDevice(uint64_t device_id);
 
   // Returns node_id of the primary active output node.
   virtual uint64_t GetPrimaryActiveOutputNode() const;
 
   // Returns the node_id of the primary active input node.
   virtual uint64_t GetPrimaryActiveInputNode() const;
 
   // Gets the audio devices back in |device_list|.
+  // This call can be invoked from I/O thread or UI thread because
+  // it does not need to access CrasAudioClient on DBus.
   virtual void GetAudioDevices(AudioDeviceList* device_list) const;
 
   virtual bool GetPrimaryActiveOutputDevice(AudioDevice* device) const;
 
   // Whether there is alternative input/output audio device.
   virtual bool has_alternative_input() const;
   virtual bool has_alternative_output() const;
 
   // Sets all active output devices' volume level to |volume_percent|, whose
   // range is from 0-100%.
@@ skipping 213 matching lines @@
   bool hdmi_rediscovering_;
 
   base::WeakPtrFactory<CrasAudioHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CrasAudioHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_