Refactors DimWindow and moves to ash/common

ash/common/wm_shell.h

Index: ash/common/wm_shell.h
diff --git a/ash/common/wm_shell.h b/ash/common/wm_shell.h
index bf5b830641778281f2227790eda0c534f0c2fc69..fbd44f1f140d75adbb5699c5677009ed235774f7 100644
--- a/ash/common/wm_shell.h
+++ b/ash/common/wm_shell.h
@@ -17,6 +17,8 @@
 #include "ash/common/wm/lock_state_observer.h"
 #include "base/observer_list.h"
 #include "ui/base/ui_base_types.h"
+#include "ui/compositor/layer_type.h"
+#include "ui/wm/public/window_types.h"
 
 namespace display {
 class Display;
@@ -155,9 +157,8 @@ class ASH_EXPORT WmShell {
     return window_selector_controller_.get();
   }
 
-  // Creates a new window used as a container of other windows. No painting is
-  // done to the created window.
-  virtual WmWindow* NewContainerWindow() = 0;
+  virtual WmWindow* NewWindow(ui::wm::WindowType window_type,
+                              ui::LayerType layer_type) = 0;
 
   virtual WmWindow* GetFocusedWindow() = 0;
   virtual WmWindow* GetActiveWindow() = 0;