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

content/public/app/BUILD.gn

 # 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.
 
 # App different than the regular content subcomponents (see comments in
 # //content/BUILD.gn) because it has to support the browser/child process split
 # (the "both" target include both browser and child process files and is used
 # for testing).
 #
 # In non-component mode, browser, child, and both all follow the same structure:
 # foo ->
 #   //content/public/app:child (group) ->
 #     //content/public/app:child_sources (source set) ->
 #       //content/app:child (source set)
 
 # In component mode, content is linked as one big turd so there is only one
 # app target containing sources ("both") and the other ones forward to it:
 # foo ->
 #   //content/public/app:child (group; "browser" and "both" ones look the same)
 #     //content (shared library) ->
 #       //content/public/app:both_sources (source set)
 
+import("//build/config/chrome_build.gni")
+
 public_app_shared_sources = [
   "content_jni_onload.h",
   "content_main.h",
   "content_main_delegate.cc",
   "content_main_delegate.h",
   "content_main_runner.h",
   "startup_helper_win.h",
 ]
 
 public_app_shared_deps = [
@@ skipping 51 matching lines @@
 
     sources = public_app_shared_sources
     configs += [ "//content:content_implementation" ]
     deps = public_app_shared_deps + [
              "//content/app:both",
              "//content/public/browser",
              "//content/public/common",
            ]
   }
 
-  # TODO(GYP) enable chrome_multiple_dll support
-  is_chrome_multiple_dll = false
-
-  if (is_chrome_multiple_dll) {
+  if (is_multi_dll_chrome) {
     source_set("browser") {
       check_includes = false  # See comment above.
 
       sources = public_app_shared_sources
 
       defines = [ "CHROME_MULTIPLE_DLL_BROWSER" ]
       configs += [ "//content:content_implementation" ]
 
       deps = public_app_shared_deps + [
                "//content/app:browser",
@@ skipping 23 matching lines @@
         ":both",
       ]
     }
     group("child") {
       deps = [
         ":both",
       ]
     }
   }
 }