Revert of 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_for_blink.typemap b/gpu/ipc/common/mailbox_holder_for_blink.typemap
deleted file mode 100644
index 976595e73d7fb682b06f0a47ad7ad2e8dde8cd21..0000000000000000000000000000000000000000
--- a/gpu/ipc/common/mailbox_holder_for_blink.typemap
+++ /dev/null
@@ -1,13 +0,0 @@
-# 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" ]
-public_deps = [
-  "//gpu/command_buffer/common",
-  "//gpu/ipc/common:interfaces",
-  "//mojo/public/cpp/bindings",
-]
-type_mappings = [ "gpu.mojom.MailboxHolder=::gpu::MailboxHolder" ]