Refactors StackingController::GetDefaultParent to ash/wm/common

ash/wm/common/BUILD.gn

 # Copyright 2016 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/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 
 assert(use_aura)
 assert(enable_hidpi)
 
 # This target contains window management code used by both mash and ash. It
 # should not use aura::Window, but may use parts of aura client code that don't
 # depend upon aura::Window directly or indirectly.
 component("ash_wm_common") {
   sources = [
     "always_on_top_controller.cc",
     "always_on_top_controller.h",
     "background_animator.cc",
     "background_animator.h",
+    "container_finder.cc",
+    "container_finder.h",
     "default_state.cc",
     "default_state.h",
     "default_window_resizer.cc",
     "default_window_resizer.h",
     "dock/docked_window_layout_manager.cc",
     "dock/docked_window_layout_manager.h",
     "dock/docked_window_layout_manager_observer.h",
     "dock/docked_window_resizer.cc",
     "dock/docked_window_resizer.h",
     "drag_details.cc",
@@ skipping 97 matching lines @@
     "//ui/keyboard",
     "//ui/views",
     "//ui/wm",
   ]
 
   if (is_win) {
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
   }
 }