DNR Prototype: With flatbuffers

extensions/browser/guest_view/app_view/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("app_view") {
   sources = [
     "app_view_constants.cc",
     "app_view_constants.h",
     "app_view_guest.cc",
     "app_view_guest.h",
     "app_view_guest_delegate.cc",
     "app_view_guest_delegate.h",
   ]
 
   deps = [
     "//content/public/common",
     "//extensions/common/api",
     "//extensions/strings",
   ]
+
+  # This is because app_view depends on guest_view and hence extensions/browser
+  # w/o declaring a dependency. See gn check out/Default
+  # extensions/browser/app_view will fail.
+  include_dirs = [ "//third_party/flatbuffers/src/include/" ]
 }