Audio input traces for Mac (browser-side)

media/audio/mac/audio_input_mac.cc

Index: media/audio/mac/audio_input_mac.cc
diff --git a/media/audio/mac/audio_input_mac.cc b/media/audio/mac/audio_input_mac.cc
index 88c6a019c6894a67e69c28429af0f4b4c619533a..8fc18d3d7807b6da332ae49d149eb3f9e05b524a 100644
--- a/media/audio/mac/audio_input_mac.cc
+++ b/media/audio/mac/audio_input_mac.cc
@@ -8,6 +8,7 @@
 
 #include "base/logging.h"
 #include "base/mac/mac_logging.h"
+#include "base/trace_event/trace_event.h"
 #include "media/audio/mac/audio_manager_mac.h"
 #include "media/base/audio_bus.h"
 
@@ -202,6 +203,7 @@ void PCMQueueInAudioInputStream::HandleInputBuffer(
     const AudioStreamPacketDescription* packet_desc) {
   DCHECK_EQ(audio_queue_, audio_queue);
   DCHECK(audio_buffer->mAudioData);
+  TRACE_EVENT0("audio", "PCMQueueInAudioInputStream::HandleInputBuffer");
   if (!callback_) {
     // This can happen if Stop() was called without start.
     DCHECK_EQ(0U, audio_buffer->mAudioDataByteSize);
@@ -220,8 +222,11 @@ void PCMQueueInAudioInputStream::HandleInputBuffer(
     // http://crbug.com/161383.
     base::TimeDelta elapsed = base::TimeTicks::Now() - last_fill_;
     const base::TimeDelta kMinDelay = base::TimeDelta::FromMilliseconds(5);
-    if (elapsed < kMinDelay)
+    if (elapsed < kMinDelay) {
+      TRACE_EVENT0("audio",
+                   "PCMQueueInAudioInputStream::HandleInputBuffer sleep");
       base::PlatformThread::Sleep(kMinDelay - elapsed);
+    }
 
     uint8_t* audio_data = reinterpret_cast<uint8_t*>(audio_buffer->mAudioData);
     audio_bus_->FromInterleaved(