Add support for multichannel playback to OpenSLES output.

media/audio/BUILD.gn

Index: media/audio/BUILD.gn
diff --git a/media/audio/BUILD.gn b/media/audio/BUILD.gn
index 617f03666b3dc75692deb10544b10d725e3c33b3..6d8a551fb708eb67d604e6140d972a4dd48c4ba8 100644
--- a/media/audio/BUILD.gn
+++ b/media/audio/BUILD.gn
@@ -188,6 +188,8 @@ source_set("audio") {
       "android/opensles_input.h",
       "android/opensles_output.cc",
       "android/opensles_output.h",
+      "android/opensles_util.cc",
+      "android/opensles_util.h",
       "android/opensles_wrapper.cc",
     ]
     deps += [ "//media/base/android:media_jni_headers" ]