Fix nested config in GN.

build/config/win/BUILD.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.
 
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 
 # Compiler setup for the Windows SDK. Applied to all targets.
 config("sdk") {
   # The include path is the stuff returned by the script.
@@ skipping 177 matching lines @@
 config("target_winrt") {
   defines = [
     "WINRT",
     "WINAPI_FAMILY=WINAPI_FAMILY_PC_APP",
   ]
   cflags_cc = [
     "/ZW",
     "/EHsc",
   ]
 }
+
+# Internal stuff --------------------------------------------------------------
+
+# Config used by the MIDL template to disable warnings.
+config("midl_warnings") {
+  if (is_clang) {
+    # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
+    cflags = [ "-Wno-extra-tokens" ]
+  }
+}

[Dirk Pranke, 2015/09/11 20:53:01]

What's the advantage to putting this here over leaving it in midl.gni?

[brettw, 2015/09/11 20:58:12]

The old way will make a new config every time you call midl(). This will fail if
you do midl() more than once, and will generate duplicate but identical configs
all over the tree.