Replace WebAudio MediaCodec usage with FFmpeg. A ~4x improvement.

content/renderer/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//content/renderer/renderer.gni")
 import("//media/media_options.gni")
 
 source_set("renderer") {
@@ skipping 75 matching lines @@
       "webscrollbarbehavior_impl_gtkoraura.cc",
       "webscrollbarbehavior_impl_gtkoraura.h",
     ]
     sources += [
       "external_popup_menu.cc",
       "external_popup_menu.h",
     ]
   }
 
   if (is_android) {
-    sources -= [ "media/audio_decoder.cc" ]
     sources += [
       "external_popup_menu.cc",
       "external_popup_menu.h",
     ]
 
     # Add back the Linux file which Android shares.
     set_sources_assignment_filter([])
     sources += [ "render_view_linux.cc" ]
 
     deps += [
@@ skipping 107 matching lines @@
       "vr/vr_dispatcher.h",
       "vr/vr_type_converters.cc",
       "vr/vr_type_converters.h",
     ]
   }
 
   if (use_seccomp_bpf) {
     defines += [ "USE_SECCOMP_BPF" ]
   }
 }