UMA log for audio_device Init and Start(Playout|Recording). Make Init return a more specific error …

webrtc/modules/audio_device/dummy/file_audio_device.h

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 30 matching lines @@
   FileAudioDevice(const int32_t id,
                   const char* inputFilename,
                   const char* outputFilename);
   virtual ~FileAudioDevice();
 
   // Retrieve the currently utilized audio layer
   int32_t ActiveAudioLayer(
       AudioDeviceModule::AudioLayer& audioLayer) const override;
 
   // Main initializaton and termination
-  int32_t Init() override;
+  InitStatus Init() override;
   int32_t Terminate() override;
   bool Initialized() const override;
 
   // Device enumeration
   int16_t PlayoutDevices() override;
   int16_t RecordingDevices() override;
   int32_t PlayoutDeviceName(uint16_t index,
                             char name[kAdmMaxDeviceNameSize],
                             char guid[kAdmMaxGuidSize]) override;
   int32_t RecordingDeviceName(uint16_t index,
@@ skipping 133 matching lines @@
   FileWrapper& _inputFile;
   std::string _outputFilename;
   std::string _inputFilename;
 
   Clock* _clock;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_AUDIO_DEVICE_FILE_AUDIO_DEVICE_H