Remove MediaStreamDeviceThread in favor of using AudioThread.

content/browser/renderer_host/media/audio_input_device_manager.cc

Index: content/browser/renderer_host/media/audio_input_device_manager.cc
diff --git a/content/browser/renderer_host/media/audio_input_device_manager.cc b/content/browser/renderer_host/media/audio_input_device_manager.cc
index 7a7ecda1f51bcb8136fdd38abab53e39b868f4af..b4959567a3179f1db9c045dbed6f5c9a9bdd0c39 100644
--- a/content/browser/renderer_host/media/audio_input_device_manager.cc
+++ b/content/browser/renderer_host/media/audio_input_device_manager.cc
@@ -13,6 +13,7 @@
 #include "media/audio/audio_manager_base.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/channel_layout.h"
+#include "media/base/scoped_histogram_timer.h"
 
 namespace content {
 
@@ -118,6 +119,8 @@ bool AudioInputDeviceManager::ShouldUseFakeDevice() const {
 
 void AudioInputDeviceManager::EnumerateOnDeviceThread(
     MediaStreamType stream_type) {
+  SCOPED_UMA_HISTOGRAM_TIMER(
+      "Media.AudioInputDeviceManager.EnumerateOnDeviceThreadTime");
   DCHECK(IsOnDeviceThread());
 
   media::AudioDeviceNames device_names;
@@ -161,6 +164,8 @@ void AudioInputDeviceManager::EnumerateOnDeviceThread(
 
 void AudioInputDeviceManager::OpenOnDeviceThread(
     int session_id, const StreamDeviceInfo& info) {
+  SCOPED_UMA_HISTOGRAM_TIMER(
+      "Media.AudioInputDeviceManager.OpenOnDeviceThreadTime");
   DCHECK(IsOnDeviceThread());
 
   StreamDeviceInfo out(info.device.type, info.device.name, info.device.id,