Adds Media.Audio.InputStartWasDeferredAudioWorkedMac UMA stat

media/audio/mac/audio_low_latency_input_mac.cc

Index: media/audio/mac/audio_low_latency_input_mac.cc
diff --git a/media/audio/mac/audio_low_latency_input_mac.cc b/media/audio/mac/audio_low_latency_input_mac.cc
index ac27f2d590488308afb0224e102a4622dd7a7bef..0599d6022580afeaa79085044a87dcb240f2ba2c 100644
--- a/media/audio/mac/audio_low_latency_input_mac.cc
+++ b/media/audio/mac/audio_low_latency_input_mac.cc
@@ -537,10 +537,25 @@ void AUAudioInputStream::Close() {
   CloseAudioUnit();
   // Disable the listener for device property changes.
   DeRegisterDeviceChangeListener();
-  // Check if any device property changes are added by filtering out a selected
-  // set of the |device_property_changes_map_| map. Add UMA stats if valuable
-  // data is found.
-  AddDevicePropertyChangesToUMA(false);
+  // Add more UMA stats but only if AGC was activated, i.e. for e.g. WebRTC
+  // audio input streams.
+  if (GetAutomaticGainControl()) {
+    // Check if any device property changes are added by filtering out a
+    // selected set of the |device_property_changes_map_| map. Add UMA stats
+    // if valuable data is found.
+    AddDevicePropertyChangesToUMA(false);
+    // Log if call to Start() was deferred or not. To be compared with

[Ilya Sherman, 2016/03/02 22:57:24]

nit: s/Log if ... or not/Log whether ...

[henrika (OOO until Aug 14), 2016/03/03 09:44:39]

Done.

+    // Media.Audio.InputStartWasDeferredMac which logs the same value but only
+    // when input audio fail to start.

[Ilya Sherman, 2016/03/02 22:57:24]

nit: s/fail/fails

[henrika (OOO until Aug 14), 2016/03/03 09:44:39]

Done.

+    UMA_HISTOGRAM_BOOLEAN("Media.Audio.InputStartWasDeferredAudioWorkedMac",
+                          start_was_deferred_);
+    // Log if a change of I/O buffer size was required. To be compared with
+    // Media.Audio.InputBufferSizeWasChangedMac which logs the same value but
+    // only when input audio fail to start.
+    UMA_HISTOGRAM_BOOLEAN("Media.Audio.InputBufferSizeWasChangedAudioWorkedMac",
+                          buffer_size_was_changed_);
+    // TODO(henrika): possibly add more values here...
+  }
   // Inform the audio manager that we have been closed. This will cause our
   // destruction.
   manager_->ReleaseInputStream(this);