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

webrtc/modules/audio_device/audio_device_generic.h

Index: webrtc/modules/audio_device/audio_device_generic.h
diff --git a/webrtc/modules/audio_device/audio_device_generic.h b/webrtc/modules/audio_device/audio_device_generic.h
index c76ea52428ad932a9a16b80abe0b0e1fc1b95dbb..b7e135ccea57ce43e5de71cf473c261727987348 100644
--- a/webrtc/modules/audio_device/audio_device_generic.h
+++ b/webrtc/modules/audio_device/audio_device_generic.h
@@ -18,12 +18,21 @@ namespace webrtc {
 
 class AudioDeviceGeneric {
  public:
+  // For use with UMA logging. Must be kept in sync with chromiums

[henrika_webrtc, 2016/06/30 08:44:20]

..."with histograms.xml in Chrome"

[Max Morin WebRTC, 2016/06/30 10:56:04]

Done.

+  // histograms.xml.
+  enum class InitStatus {
+    kOk = 0,

[henrika_webrtc, 2016/06/30 08:44:20]

don't we use the Google C++ code style? 
Like: OK, PLAYOUT_ERROR etc.

[Max Morin WebRTC, 2016/06/30 10:56:04]

Done.

+    kPlayoutError = 1,
+    kRecordingError = 2,
+    kOtherError = 3,
+    kNumStatuses = 4
+  };
   // Retrieve the currently utilized audio layer
   virtual int32_t ActiveAudioLayer(
       AudioDeviceModule::AudioLayer& audioLayer) const = 0;
 
   // Main initializaton and termination
-  virtual int32_t Init() = 0;
+  virtual InitStatus Init() = 0;
   virtual int32_t Terminate() = 0;
   virtual bool Initialized() const = 0;