Chrome 18 specific fix for fixing HTML5 audio output on Mac.

content/renderer/media/audio_device.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 "content/renderer/media/audio_device.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/time.h"
@@ skipping 77 matching lines @@
   // this class.
   CHECK_EQ(0, stream_id_);
   for (int i = 0; i < channels_; ++i)
     delete [] audio_data_[i];
 }
 
 void AudioDevice::Start() {
   AudioParameters params;
   params.format = latency_format_;
   params.channels = channels_;
+
+  // Chrome 18 specific fix for http://crbug.com/109441 where we determine the
+  // ChannelLayout based on |channels_| but only up to stereo. The proper fix
+  // was committed as r128054 in time for Chrome 19 but it's not suitable for
+  // merging.
+  //
+  // NOTE: surround sound will still be broken but that's something we'll have
+  // to live with until Chrome 19.
+  if (channels_ == 1) {
+    params.channel_layout = CHANNEL_LAYOUT_MONO;
+  } else if (channels_ == 2) {
+    params.channel_layout = CHANNEL_LAYOUT_STEREO;
+  } else {
+    params.channel_layout = CHANNEL_LAYOUT_NONE;
+  }
+
   params.sample_rate = static_cast<int>(sample_rate_);
   params.bits_per_sample = bits_per_sample_;
   params.samples_per_packet = buffer_size_;
 
   ChildProcess::current()->io_message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&AudioDevice::InitializeOnIOThread, this, params));
 }
 
 void AudioDevice::Stop() {
@@ skipping 222 matching lines @@
     // audio thread.
     audio_socket_->Close();
     audio_thread_->Join();
     // Make sure not to release the socket pointer until after the thread
     // has exited.  Otherwise there's a race between startup of the thread
     // and this.
     audio_socket_ = NULL;
     audio_thread_.reset(NULL);
   }
 }