Refactors DimWindow and moves to ash/common

ash/wm/screen_dimmer_unittest.cc

 // Copyright (c) 2012 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.
 
 #include "ash/wm/screen_dimmer.h"
 
 #include <memory>
 
+#include "ash/aura/wm_window_aura.h"
+#include "ash/common/wm/window_dimmer.h"
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
-#include "ash/wm/dim_window.h"
-//#include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/test/test_windows.h"
 #include "ui/compositor/layer.h"
 
 namespace ash {
 namespace test {
 
 class ScreenDimmerTest : public AshTestBase {
  public:
   ScreenDimmerTest() : dimmer_(nullptr) {}
   ~ScreenDimmerTest() override {}
 
   void SetUp() override {
     AshTestBase::SetUp();
     dimmer_ = ScreenDimmer::GetForRoot();
   }
 
   aura::Window* GetDimWindow() {
-    return DimWindow::Get(Shell::GetPrimaryRootWindow());
+    WindowDimmer* window_dimmer =
+        WindowDimmer::Get(WmWindowAura::Get(Shell::GetPrimaryRootWindow()));
+    return window_dimmer ? WmWindowAura::GetAuraWindow(window_dimmer->window())
+                         : nullptr;
   }
 
   ui::Layer* GetDimWindowLayer() {
     aura::Window* window = GetDimWindow();
     return window ? window->layer() : nullptr;
   }
 
  protected:
   ScreenDimmer* dimmer_;  // not owned
 
@@ skipping 70 matching lines @@
 
   dim_iter = std::find(root_window->children().begin(),
                        root_window->children().end(), GetDimWindow());
   ASSERT_TRUE(dim_iter != root_window->children().end());
   // Dom layer is at the bottom.
   EXPECT_EQ(*dim_iter, *root_window->children().begin());
 }
 
 }  // namespace test
 }  // namespace ash