Re-land^2 WebVR compositor bypass via BrowserMain context + mailbox

gpu/ipc/common/mailbox_holder_for_blink.typemap

Index: gpu/ipc/common/mailbox_holder_for_blink.typemap
diff --git a/gpu/ipc/common/mailbox_holder.typemap b/gpu/ipc/common/mailbox_holder_for_blink.typemap
similarity index 67%
copy from gpu/ipc/common/mailbox_holder.typemap
copy to gpu/ipc/common/mailbox_holder_for_blink.typemap
index 4644f3219d3eb24c3af8783de3fb6a91e041bbc8..976595e73d7fb682b06f0a47ad7ad2e8dde8cd21 100644
--- a/gpu/ipc/common/mailbox_holder.typemap
+++ b/gpu/ipc/common/mailbox_holder_for_blink.typemap
@@ -1,11 +1,13 @@
-# Copyright 2016 The Chromium Authors. All rights reserved.
+# Copyright 2017 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.
 
 mojom = "//gpu/ipc/common/mailbox_holder.mojom"
 public_headers = [ "//gpu/command_buffer/common/mailbox_holder.h" ]
 traits_headers = [ "//gpu/ipc/common/mailbox_holder_struct_traits.h" ]
-deps = [
-  "//gpu/ipc/common:struct_traits",
+public_deps = [
+  "//gpu/command_buffer/common",
+  "//gpu/ipc/common:interfaces",
+  "//mojo/public/cpp/bindings",
 ]
 type_mappings = [ "gpu.mojom.MailboxHolder=::gpu::MailboxHolder" ]