Add mojo interface for audio rendering.

content/browser/BUILD.gn

Index: content/browser/BUILD.gn
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index ffe68664e4a32afdaa0b1747449c364fba841ebe..57e294c851cfee6e3adb8a8636dc2855f312b762 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -1109,6 +1109,11 @@ source_set("browser") {
     "renderer_host/media/audio_output_delegate.h",
     "renderer_host/media/audio_output_delegate_impl.cc",
     "renderer_host/media/audio_output_delegate_impl.h",
+    "renderer_host/media/audio_output_impl.cc",
+    "renderer_host/media/audio_output_impl.h",
+    "renderer_host/media/audio_output_service_context.h",
+    "renderer_host/media/audio_output_service_context_impl.cc",
+    "renderer_host/media/audio_output_service_context_impl.h",
     "renderer_host/media/audio_renderer_host.cc",
     "renderer_host/media/audio_renderer_host.h",
     "renderer_host/media/audio_sync_reader.cc",
@@ -1129,6 +1134,8 @@ source_set("browser") {
     "renderer_host/media/media_stream_track_metrics_host.h",
     "renderer_host/media/media_stream_ui_proxy.cc",
     "renderer_host/media/media_stream_ui_proxy.h",
+    "renderer_host/media/render_frame_audio_output_service.cc",
+    "renderer_host/media/render_frame_audio_output_service.h",
     "renderer_host/media/video_capture_controller.cc",
     "renderer_host/media/video_capture_controller.h",
     "renderer_host/media/video_capture_controller_event_handler.h",