Add a GN flag for the Windows multi-dll build.

build/secondary/tools/grit/grit_rule.gni

 # Copyright 2014 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.
 
 # Instantiate grit. This will produce a script target to run grit, and a
 # static library that compiles the .cc files.
 #
 # Parameters
 #
 #   source (required)
@@ skipping 57 matching lines @@
 #     source = "myfile.grd"
 #     outputs = [
 #       "foo_strings.h",
 #       "foo_strings.pak",
 #     ]
 #
 #     grit_flags = [ "-E", "foo=bar" ]  # Optional extra flags.
 #     # You can also put deps here if the grit source depends on generated
 #     # files.
 #   }
+import("//build/config/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 
 grit_defines = []
 
 # Mac and iOS want Title Case strings.
 use_titlecase_in_grd_files = is_mac || is_ios
 if (use_titlecase_in_grd_files) {
   grit_defines += [
@@ skipping 370 matching lines @@
     if (defined(invoker.configs)) {
       configs += invoker.configs
     }
 
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
     output_name = grit_output_name
   }
 }