Add mailbox-based Mojo VideoFrame variant.

media/mojo/common/BUILD.gn

 # Copyright 2016 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.
 
 source_set("common") {
   sources = [
     "media_type_converters.cc",
     "media_type_converters.h",
     "mojo_decoder_buffer_converter.cc",
     "mojo_decoder_buffer_converter.h",
     "mojo_shared_buffer_video_frame.cc",
     "mojo_shared_buffer_video_frame.h",
   ]
 
   deps = [
     "//base",
+    "//gpu/ipc/common:struct_traits",

[sandersd (OOO until July 31), 2017/01/19 19:40:48]

I'm not actually sure whether this is required. That said, I think there are
some GPU things I used without pulling them in, and that worked, so I'm not sure
what the dependency tree actually looks like.

     "//media",
     "//media/mojo/interfaces",
     "//mojo/common",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//ui/gfx/geometry",
     "//ui/gfx/geometry/mojo",
   ]
 }