Make ui gn check pass. Misc GN build improvements.

ui/aura/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")
 
 component("aura") {
   sources = [
     "client/aura_constants.cc",
     "client/aura_constants.h",
@@ skipping 165 matching lines @@
     "//skia",
     "//testing/gtest",
     "//ui/base",
     "//ui/base:test_support",
     "//ui/compositor:test_support",
     "//ui/events",
     "//ui/events:events_base",
     "//ui/events:test_support",
     "//ui/gfx",
     "//ui/gfx/geometry",
+    "//ui/wm",
   ]
 
   if (is_win) {
     cflags = [
       "/wd4267", # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     ]
   }
 
   if (use_aura) {
     if (is_win) {
@@ skipping 97 matching lines @@
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 
   if (is_linux) {
     deps += [
       "//third_party/mesa",
     ]
   }
 }