Try not to let the AUHAL driver get stuck sending silence.

media/audio/mac/audio_auhal_mac.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/mac/audio_auhal_mac.h"
 
 #include <CoreServices/CoreServices.h>
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
@@ skipping 54 matching lines @@
       params_(params),
       input_channels_(params_.input_channels()),
       output_channels_(params_.channels()),
       number_of_frames_(params_.frames_per_buffer()),
       source_(NULL),
       device_(device),
       audio_unit_(0),
       volume_(1),
       hardware_latency_frames_(0),
       stopped_(false),
+      notified_for_possible_device_change_(false),
       input_buffer_list_(NULL) {
   // We must have a manager.
   DCHECK(manager_);
 
   VLOG(1) << "AUHALStream::AUHALStream()";
   VLOG(1) << "Device: " << device;
   VLOG(1) << "Input channels: " << input_channels_;
   VLOG(1) << "Output channels: " << output_channels_;
   VLOG(1) << "Sample rate: " << params_.sample_rate();
   VLOG(1) << "Buffer size: " << number_of_frames_;
@@ skipping 67 matching lines @@
 }
 
 void AUHALStream::Start(AudioSourceCallback* callback) {
   DCHECK(callback);
   if (!audio_unit_) {
     DLOG(ERROR) << "Open() has not been called successfully";
     return;
   }
 
   stopped_ = false;
+  notified_for_possible_device_change_ = false;
   {
     base::AutoLock auto_lock(source_lock_);
     source_ = callback;
   }
 
   AudioOutputUnitStart(audio_unit_);
 }
 
 void AUHALStream::Stop() {
   if (stopped_)
@@ skipping 30 matching lines @@
     // This can happen if we've suddenly changed sample-rates.
     // The stream should be stopping very soon.
     //
     // Unfortunately AUAudioInputStream and AUHALStream share the frame
     // size set by kAudioDevicePropertyBufferFrameSize above on a per process
     // basis.  What this means is that the |number_of_frames| value may be
     // larger or smaller than the value set during ConfigureAUHAL().
     // In this case either audio input or audio output will be broken,
     // so just output silence.
     ZeroBufferList(io_data);
+
+    // In case we missed a device notification, notify the AudioManager that the
+    // device has changed.  HandleDeviceChanges() will check to make sure the
+    // device has actually changed before taking any action.
+    if (!notified_for_possible_device_change_) {
+      notified_for_possible_device_change_ = true;
+      manager_->GetMessageLoop()->PostTask(FROM_HERE, base::Bind(
+          &AudioManagerMac::HandleDeviceChanges, base::Unretained(manager_)));
+    }
+
     return noErr;
   }
 
   if (input_channels_ > 0 && input_buffer_list_) {
     // Get the input data.  |input_buffer_list_| is wrapped
     // to point to the data allocated in |input_bus_|.
     OSStatus result = AudioUnitRender(
         audio_unit_,
         flags,
         output_time_stamp,
@@ skipping 299 matching lines @@
       0,
       &callback,
       sizeof(callback));
   if (result != noErr)
     return false;
 
   return true;
 }
 
 }  // namespace media