Refactors DimWindow and moves to ash/common

ash/wm/screen_dimmer.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 "ash/aura/wm_window_aura.h"
+#include "ash/common/wm/window_dimmer.h"
 #include "ash/common/wm_shell.h"
 #include "ash/shell.h"
-#include "ash/wm/dim_window.h"
 #include "base/time/time.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_property.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 
 DECLARE_WINDOW_PROPERTY_TYPE(ash::ScreenDimmer*);
 
@@ skipping 64 matching lines @@
              ? primary
              : primary->GetChildById(container_id);
 }
 
 void ScreenDimmer::OnRootWindowAdded(WmWindow* root_window) {
   Update(is_dimming_);
 }
 
 void ScreenDimmer::Update(bool should_dim) {
   for (aura::Window* container : GetAllContainers(container_id_)) {
-    DimWindow* dim = DimWindow::Get(container);
+    WindowDimmer* dim = WindowDimmer::Get(WmWindowAura::Get(container));
     if (should_dim) {
       if (!dim) {
-        dim = new DimWindow(container);
+        dim = new WindowDimmer(WmWindowAura::Get(container));

[James Cook, 2016/09/09 00:03:36]

Or maybe ScreenDimmer could store a set of WindowDimmers. The ownership here is
tricky -- this looks leaky, but isn't.

[sky, 2016/09/09 03:50:04]

You're right that I could be more explicit and maintain a
map<WmWindow*,WindowDimmer> directly and get rid of the UserData. But that would
mean that logic is required for all consumers. (ScreenPinningController also
uses WindowDimmer). Going with UserData seemed less code, a better match for
what we have now, at the expense of dual ownership.

         dim->SetDimOpacity(target_opacity_);
       }
       if (at_bottom_)
-        dim->parent()->StackChildAtBottom(dim);
+        dim->parent()->StackChildAtBottom(dim->window());
       else
-        dim->parent()->StackChildAtTop(dim);
-      dim->Show();
-    } else {
-      if (dim) {
-        dim->Hide();
-        delete dim;
-      }
+        dim->parent()->StackChildAtTop(dim->window());
+      dim->window()->Show();
+    } else if (dim) {
+      dim->Destroy();
     }
   }
 }
 
 }  // namespace ash