Support more than 8 channels for AudioContext.destination node on OSX

content/renderer/renderer_blink_platform_impl.cc

Index: content/renderer/renderer_blink_platform_impl.cc
diff --git a/content/renderer/renderer_blink_platform_impl.cc b/content/renderer/renderer_blink_platform_impl.cc
index 9130436578d442e3e57a31042b4aa220484aa5e3..f3d13a70e7ed519f11628450181dbdb14e909d49 100644
--- a/content/renderer/renderer_blink_platform_impl.cc
+++ b/content/renderer/renderer_blink_platform_impl.cc
@@ -701,8 +701,6 @@ WebAudioDevice* RendererBlinkPlatformImpl::createAudioDevice(
   // The |channels| does not exactly identify the channel layout of the
   // device. The switch statement below assigns a best guess to the channel
   // layout based on number of channels.
-  // TODO(crogers): WebKit should give the channel layout instead of the hard

[Raymond Toy, 2015/01/08 21:55:54]

This TODO is still true isn't it?  WebKit does still give the channel count and
not the layout, right?

[hongchan, 2015/01/08 21:58:33]

Still true for WebKit, but here at Blink we have the implementation of
CHANNEL_LAYOUT_*. I thought it only applies to WebKit and the comment is
outdated - but I don't mind reverting the comment back.

[Raymond Toy, 2015/01/08 22:02:57]

But creatAudioDevice still takes unsigned channels, and not some kind of channel
layout enum or object. I think that's what the comment is referring to. 
(Substitute Blink for WebKit).

-  // channel count.
   media::ChannelLayout layout = media::CHANNEL_LAYOUT_UNSUPPORTED;
   switch (channels) {
     case 1:
@@ -730,7 +728,9 @@ WebAudioDevice* RendererBlinkPlatformImpl::createAudioDevice(
       layout = media::CHANNEL_LAYOUT_7_1;
       break;
     default:
-      layout = media::CHANNEL_LAYOUT_STEREO;
+      // If the layout is not supported (more than 9 channels), falls back to
+      // discrete mode.
+      layout = media::CHANNEL_LAYOUT_DISCRETE;
   }
 
   int session_id = 0;
@@ -742,9 +742,11 @@ WebAudioDevice* RendererBlinkPlatformImpl::createAudioDevice(
     input_channels = 0;
   }
 
+  // For CHANNEL_LAYOUT_DISCRETE, pass the explicit channel count along with
+  // the channel layout when creating an |AudioParameters| object.
   media::AudioParameters params(
       media::AudioParameters::AUDIO_PCM_LOW_LATENCY,
-      layout, static_cast<int>(sample_rate), 16, buffer_size,
+      layout, channels, static_cast<int>(sample_rate), 16, buffer_size,
       media::AudioParameters::NO_EFFECTS);
 
   return new RendererWebAudioDeviceImpl(params, callback, session_id);