Fixes audio issue on Mac for USB headsets

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 4d8de904654aef911933ade5629d520e871b7def..1894ead7dcd30d875d09605b9e053fd0f023aec9 100644
--- a/media/audio/mac/audio_low_latency_input_mac.cc
+++ b/media/audio/mac/audio_low_latency_input_mac.cc
@@ -496,7 +496,14 @@ OSStatus AUAudioInputStream::InputProc(void* user_data,
   if (result) {
     UMA_HISTOGRAM_SPARSE_SLOWLY("Media.AudioInputCbErrorMac", result);
     OSSTATUS_DLOG(ERROR, result) << "AudioUnitRender() failed ";
-    audio_input->HandleError(result);
+    if (result != kAudioUnitErr_TooManyFramesToProcess) {
+      // We avoid stopping the stream for kAudioUnitErr_TooManyFramesToProcess
+      // since it has been observed that some USB headsets can cause this error
+      // but only for a few initial frames at startup and then then the stream

[DaleCurtis, 2015/03/18 22:09:06]

Since you explicitly mention that this returns to normal shortly, can you add a
backoff count which fires an error once a threshold is hit?

[no longer working on chromium, 2015/03/18 22:15:01]

It is a bit hard to define the threshold since it depends on the device, sort of
timing things related to ramp change.

How about adding a uma stat to get some understanding?

+      // returns to a stable state again.
+      // See b/19524368 for details.
+      audio_input->HandleError(result);
+    }
     return result;
   }