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

remoting/webapp/build_template.gni

 # Copyright 2015 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.
 
 # Keep in sync with 'remoting_webapp' target in remoting/remoting_client.gypi.
 
+import("//build/config/chrome_build.gni")
 import("//remoting/remoting_locales.gni")
 import("//remoting/remoting_options.gni")
 import("//remoting/remoting_version.gni")
 import("//remoting/webapp/files.gni")
 
 # The base remoting directory that is used as the root directory for file
 # references. Many of the scripts rely on the files being specified relative
 # to this directory.
 remoting_dir = "//remoting"
 
@@ skipping 80 matching lines @@
     args += [
       "--locales_listfile",
       listfile_rel,
     ]
     args += [
       "--use_gcd",
       "$remoting_use_gcd",
     ]
   }
 }