Fix WebAudio support for discrete channel layouts.

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 ed61cd8eea512033476ff67fa45198fe395d2e9b..6c4823db43cfd6506fb27afb724f18a958e2f9f8 100644
--- a/content/renderer/renderer_blink_platform_impl.cc
+++ b/content/renderer/renderer_blink_platform_impl.cc
@@ -675,49 +675,18 @@ 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.
-  media::ChannelLayout layout = media::CHANNEL_LAYOUT_UNSUPPORTED;
-  switch (channels) {
-    case 1:
-      layout = media::CHANNEL_LAYOUT_MONO;
-      break;
-    case 2:
-      layout = media::CHANNEL_LAYOUT_STEREO;
-      break;
-    case 3:
-      layout = media::CHANNEL_LAYOUT_2_1;

[DaleCurtis, 2017/02/21 22:22:44]

New code will return SURROUND here:

Old: Front L, Front R, Back C
New: Front L, Front R, Front C

-      break;
-    case 4:
-      layout = media::CHANNEL_LAYOUT_4_0;

[DaleCurtis, 2017/02/21 22:22:44]

New code will return QUAD here:

Old: Front L, Front R, Front C, Back C
New: Front L, Front R, Back L, Back R

-      break;
-    case 5:
-      layout = media::CHANNEL_LAYOUT_5_0;
-      break;
-    case 6:
-      layout = media::CHANNEL_LAYOUT_5_1;
-      break;
-    case 7:
-      layout = media::CHANNEL_LAYOUT_7_0;

[DaleCurtis, 2017/02/21 22:22:44]

New code will return 6.1 here:

Old: Front L, Front R, Front C, Side L, Side R, Front LofC, Front RofC
New: Front L, Front R, Front C, LFE, Side L, Side R, Rear Center

-      break;
-    case 8:
-      layout = media::CHANNEL_LAYOUT_7_1;
-      break;
-    default:
-      // TODO need to also pass 'channels' into RendererWebAudioDeviceImpl for
-      // CHANNEL_LAYOUT_DISCRETE
-      NOTREACHED();
-  }
+  media::ChannelLayout layout = media::GuessChannelLayout(channels);
+  if (layout == media::CHANNEL_LAYOUT_UNSUPPORTED)
+    layout = media::CHANNEL_LAYOUT_DISCRETE;
 
-  int session_id = 0;
+  int session_id;
   if (input_device_id.isNull() ||
       !base::StringToInt(input_device_id.utf8(), &session_id)) {

[DaleCurtis, 2017/02/21 22:22:44]

Note: This method may write to |session_id| even when failing, so the old path
was incorrect. It needs to clear session_id if the conversion fails.
|input_channels| is not used and I don't think the DLOG was adding anything, so
removed too.

-    if (input_channels > 0)
-      DLOG(WARNING) << "createAudioDevice(): request for audio input ignored";
-
-    input_channels = 0;
+    session_id = 0;
   }
 
   return RendererWebAudioDeviceImpl::Create(
-      layout, latency_hint, callback, session_id,
+      layout, channels, latency_hint, callback, session_id,
       static_cast<url::Origin>(security_origin));
 }