Add GN files for google_update target.

google_update/BUILD.gn

+# 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.
+
+import("//build/toolchain/win/midl.gni")
+
+config("google_update_config") {
+  include_dirs = [ "$root_gen_dir" ]

[Slava Chigrin, 2015/01/14 19:08:17]

Used root_gen_dir instead of target_gen_dir because of chrome includes file like
that
#include "google_update/google_update_idl.h"
See
https://code.google.com/p/chromium/codesearch#search/&q=google_update_idl.h&s...

[robertshield, 2015/01/14 19:30:06]

I don't really know how GN works, but if this is worth mentioning here, is it
also worth placing in a comment?

[Slava Chigrin, 2015/01/14 20:14:29]

Done.

+}
+
+midl("google_update_idl") {
+  sources = [
+    "google_update_idl.idl",
+  ]
+}
+
+static_library("google_update") {
+  sources = [
+    "$target_gen_dir/google_update_idl.h",
+    "$target_gen_dir/google_update_idl_i.c",
+  ]
+
+  public_configs = [ ":google_update_config" ]
+
+  deps = [
+    ":google_update_idl",
+  ]
+}