Adds input device selection on Windows.

media/audio/win/audio_low_latency_input_win.h

Index: media/audio/win/audio_low_latency_input_win.h
===================================================================
--- media/audio/win/audio_low_latency_input_win.h	(revision 112958)
+++ media/audio/win/audio_low_latency_input_win.h	(working copy)
@@ -78,7 +78,7 @@
   // the audio manager who is creating this object.
   WASAPIAudioInputStream(AudioManagerWin* manager,
                          const AudioParameters& params,
-                         ERole device_role);
+                         const std::string& device_id);
   // The dtor is typically called by the AudioManager only and it is usually
   // triggered by calling AudioInputStream::Close().
   virtual ~WASAPIAudioInputStream();
@@ -103,7 +103,7 @@
   void HandleError(HRESULT err);
 
   // The Open() method is divided into these sub methods.
-  HRESULT SetCaptureDevice(ERole device_role);
+  HRESULT SetCaptureDevice();
   HRESULT ActivateCaptureDevice();
   HRESULT GetAudioEngineStreamFormat();
   bool DesiredFormatIsSupported();
@@ -145,8 +145,10 @@
   // Length of the audio endpoint buffer.
   size_t endpoint_buffer_size_frames_;
 
-  // Defines the role that the system has assigned to an audio endpoint device.
-  ERole device_role_;
+  // Contains the unique name of the selected endpoint device.
+  // Note that AudioManagerBase::kDefaultDeviceId represents the default
+  // device role and is not a valid ID as such.
+  std::string device_id_;
 
   // Conversion factor used in delay-estimation calculations.
   // Converts a raw performance counter value to 100-nanosecond unit.