Prevent AudioLowLatencyInputMac from changing frame sizes.

media/audio/mac/audio_low_latency_input_mac.cc

 // Copyright (c) 2012 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_low_latency_input_mac.h"
 
 #include <CoreServices/CoreServices.h>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
@@ skipping 177 matching lines @@
                                 kAudioUnitScope_Output,
                                 1,
                                 &format_,
                                 sizeof(format_));
   if (result) {
     HandleError(result);
     return false;
   }
 
   // Set the desired number of frames in the IO buffer (output scope).
+  // WARNING: Setting this value changes the frame size for all audio units in
+  // the current process.  It's imperative that the input and output frame sizes
+  // be the same as audio_util::GetAudioHardwareBufferSize().
+  // TODO(henrika): Due to http://crrev.com/159666 this is currently not true
+  // and should be fixed, a CHECK() should be added at that time.
   result = AudioUnitSetProperty(audio_unit_,
                                 kAudioDevicePropertyBufferFrameSize,
                                 kAudioUnitScope_Output,
                                 1,
                                 &number_of_frames_,  // size is set in the ctor
                                 sizeof(number_of_frames_));
   if (result) {
     HandleError(result);
     return false;
   }
@@ skipping 393 matching lines @@
     kAudioDevicePropertyScopeInput,
     static_cast<UInt32>(channel)
   };
   OSStatus result = AudioObjectIsPropertySettable(input_device_id_,
                                                   &property_address,
                                                   &is_settable);
   return (result == noErr) ? is_settable : false;
 }
 
 }  // namespace media