Add GN files for google_update target.

Review URL: https://codereview.chromium.org/853643004

Cr-Commit-Position: refs/heads/master@{#311547}

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") {
+  # Chromium uses include paths like "google_update/google_update_idl.h",
+  # so add root_gen_dir, rather then target_gen_dir to include dirs.
+  include_dirs = [ "$root_gen_dir" ]
+}
+
+midl("google_update_idl") {
+  sources = [
+    "google_update_idl.idl",
+  ]
+}
+
+static_library("google_update") {
+  sources = [
+    "$target_gen_dir/google_update_idl.h",
+    "$target_gen_dir/google_update_idl_i.c",
+  ]
+
+  public_configs = [ ":google_update_config" ]
+
+  deps = [
+    ":google_update_idl",
+  ]
+}