Hook up GN official build and branding.

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 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.
 
 # =============================================================================
 # BUILD FLAGS
 # =============================================================================
 #
 # This block lists input arguments to the build, along with their default
 # values. GN requires listing them explicitly so it can validate input and have
@@ skipping 37 matching lines @@
   # Setting this flag will override this logic and generate 64-bit toolchains.
   #
   # Normally this would get set automatically when you specify a target using
   # the 64-bit toolchain. You can also set this on the command line to convert
   # the default toolchain to 64-bit.
   force_win64 = false
 
   # Set to true on the command line when invoked by GYP. Build files can key
   # off of this to make any GYP-output-specific changes to the build.
   is_gyp = false
+
+  # Selects the desired build flavor. Official builds get additional
+  # processing to prepare for release. Normally you will want to develop and
+  # test with this flag off.
+  is_official_build = false
+
+  # Select the desired branding flavor. False means normal Chromium branding,
+  # true means official Google Chrome branding (requires extra Google-internal
+  # resources).
+  is_chrome_branded = false
 }
 
 # =============================================================================
 # OS DEFINITIONS
 # =============================================================================
 #
 # We set these various is_FOO booleans for convenience in writing OS-based
 # conditions.
 #
 # - is_android, is_chromeos, is_ios, and is_win should be obvious.
@@ skipping 339 matching lines @@
     set_default_toolchain("//build/toolchain/linux:arm")
   } else if (build_cpu_arch == "x86") {
     set_default_toolchain("//build/toolchain/linux:32")
   } else if (build_cpu_arch == "x64") {
     set_default_toolchain("//build/toolchain/linux:64")
   }
 } else if (is_mac) {
   host_toolchain = "//build/toolchain/mac:clang"
   set_default_toolchain(host_toolchain)
 }