Move window_manager service implementation to //services

services/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.
 
+import("//build/config/ui.gni")
+
 group("services") {
   deps = [
     "//services/http_server",
     "//services/http_server/public",
     "//services/js",
     "//services/tracing",
   ]
+
+  if (use_aura) {
+    deps += [
+      "//services/window_manager",
+    ]
+  }
 }