cc: Make separate interface for BeginFrame ipc from OutputSurface

content/content_renderer.gypi

Index: content/content_renderer.gypi
diff --git a/content/content_renderer.gypi b/content/content_renderer.gypi
index d3f0e19fe7141c4cede40911f893e9c24de4b99f..46c5299fd0739cb88b897a5c9be85e256b9977a4 100644
--- a/content/content_renderer.gypi
+++ b/content/content_renderer.gypi
@@ -160,6 +160,10 @@
       'renderer/gamepad_shared_memory_reader.h',
       'renderer/geolocation_dispatcher.cc',
       'renderer/geolocation_dispatcher.h',
+      'renderer/gpu/compositor_external_begin_frame_source.cc',
+      'renderer/gpu/compositor_external_begin_frame_source.h',
+      'renderer/gpu/compositor_forwarding_message_filter.cc',
+      'renderer/gpu/compositor_forwarding_message_filter.h',
       'renderer/gpu/compositor_output_surface.cc',
       'renderer/gpu/compositor_output_surface.h',
       'renderer/gpu/compositor_software_output_device.cc',