Use enclosing rect to find WindowTreeHost size.

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")
 import("//testing/test.gni")
 
 component("aura") {
   sources = [
     "../wm/public/activation_change_observer.cc",
@@ skipping 243 matching lines @@
     deps += [ "//ui/gfx/x" ]
   }
 }
 
 test("aura_unittests") {
   sources = [
     "gestures/gesture_recognizer_unittest.cc",
     "test/run_all_unittests.cc",
     "window_event_dispatcher_unittest.cc",
     "window_targeter_unittest.cc",
+    "window_tree_host_unittest.cc",
     "window_unittest.cc",
   ]
 
   deps = [
     ":test_support",
     "//base/test:test_support",
     "//skia",
     "//testing/gtest",
     "//ui/base:test_support",
     "//ui/compositor:test_support",
     "//ui/display:test_support",
     "//ui/events:gesture_detection",
     "//ui/events:test_support",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl:test_support",
   ]
 
   if (is_linux) {
     deps += [ "//third_party/mesa" ]
   }
 
   data_deps = [
     "//third_party/mesa:osmesa",
   ]
 }