(Relanding) Restores larger output buffer size when output stream requiring smaller size is closed

media/audio/mac/audio_auhal_mac.cc

Index: media/audio/mac/audio_auhal_mac.cc
diff --git a/media/audio/mac/audio_auhal_mac.cc b/media/audio/mac/audio_auhal_mac.cc
index d71673fd12ae517dd61f0fdedabda64d2e7e4077..174eb4518f0ceff5199f2475e53d300c93096875 100644
--- a/media/audio/mac/audio_auhal_mac.cc
+++ b/media/audio/mac/audio_auhal_mac.cc
@@ -122,6 +122,11 @@ void AUHALStream::Close() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(1) << "Close";
   CloseAudioUnit();
+  // Notify the audio manager about an upcoming call to ReleaseOutputStream()
+  // and also provide the device ID of the utilized audio device. This is a
+  // trick to ensure that the audio manager only tries to increase the native
+  // I/O buffer size for real audio streams and not for e.g. fake streams.
+  manager_->PrepareForAttemptToIncreaseIOBufferSize(device_);

[o1ka, 2016/05/12 11:30:17]

Ah ok, I see what you mean. Could we simplify it a bit by just having a
dedicated method ReleaseOutputStream(stream, device) in the manager? Than we can
get rid of both device_id_used_by_closing_output_stream_ and
try_to_increase_io_buffer_size_, and make a single call here.

[o1ka, 2016/05/12 12:04:15]

(Actually, it should be named differently, because overloading is not encouraged
by Chromium if I'm not mistaken)

[henrika (OOO until Aug 14), 2016/05/12 13:02:08]

Well, that does not seem that strict but OK I can change it ;-)

[henrika (OOO until Aug 14), 2016/05/12 13:02:08]

Good idea. Done.

   // Inform the audio manager that we have been closed. This will cause our
   // destruction.
   manager_->ReleaseOutputStream(this);
@@ -175,6 +180,7 @@ void AUHALStream::Stop() {
   if (stopped_)
     return;
   DVLOG(1) << "Stop";
+  DVLOG(2) << "number_of_frames: " << number_of_frames_;
   OSStatus result = AudioOutputUnitStop(audio_unit_);
   OSSTATUS_DLOG_IF(ERROR, result != noErr, result)
       << "AudioOutputUnitStop() failed.";
@@ -218,8 +224,7 @@ OSStatus AUHALStream::Render(
       // changes reflected in UMA stats.
       number_of_frames_requested_ = number_of_frames;
       DVLOG(1) << "Audio frame size changed from " << number_of_frames_
-               << " to " << number_of_frames
-               << "; adding FIFO to compensate.";
+               << " to " << number_of_frames << " adding FIFO to compensate.";
       audio_fifo_.reset(new AudioPullFifo(
           output_channels_,
           number_of_frames_,