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

chrome/browser/android/vr_shell/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.
 
 import("//build/config/android/rules.gni")
 import("//chrome/common/features.gni")
 import("//testing/test.gni")
 
 assert(enable_webvr)
 
 if (current_cpu == "arm" || current_cpu == "arm64") {
   static_library("vr_common") {
     defines = []
 
     sources = [
       "android_ui_gesture_target.cc",
       "android_ui_gesture_target.h",
       "animation.cc",
       "animation.h",
       "easing.cc",
       "easing.h",
+      "mailbox_to_surface_bridge.cc",
+      "mailbox_to_surface_bridge.h",
       "non_presenting_gvr_delegate.cc",
       "non_presenting_gvr_delegate.h",
       "ui_elements.cc",
       "ui_elements.h",
       "ui_interface.cc",
       "ui_interface.h",
       "ui_scene.cc",
       "ui_scene.h",
       "vr_compositor.cc",
       "vr_compositor.h",
@@ skipping 33 matching lines @@
       "//base",
       "//cc",
       "//components/omnibox/browser",
       "//components/rappor",
       "//components/security_state/core",
       "//content/public/android:jni",
       "//content/public/browser",
       "//content/public/common",
       "//device/gamepad",
       "//device/vr",
+      "//services/ui/public/cpp/gpu",
       "//ui/android",
       "//ui/base",
       "//ui/display",
       "//ui/gl",
       "//ui/gl/init",
     ]
 
     libs = [
       "//third_party/gvr-android-sdk/libgvr_shim_static_${current_cpu}.a",
       "android",
@@ skipping 21 matching lines @@
       ":vr_common",
       "//base/test:run_all_unittests",
       "//base/test:test_support",
       "//chrome/browser",
       "//testing/gtest",
       "//third_party/WebKit/public:blink",
       "//ui/gfx/geometry",
     ]
   }
 }