Renames WmWindowUserData and converts to using aura

ash/common/wm/window_dimmer.h

Index: ash/common/wm/window_dimmer.h
diff --git a/ash/common/wm/window_dimmer.h b/ash/common/wm/window_dimmer.h
index 48ded9775d9393c43dd52d45331a2f8e77aa1598..bb6aad825b07b7a2c0692b4297245e1a565534a4 100644
--- a/ash/common/wm/window_dimmer.h
+++ b/ash/common/wm/window_dimmer.h
@@ -5,14 +5,14 @@
 #ifndef ASH_COMMON_WINDOW_DIMMER_H_
 #define ASH_COMMON_WINDOW_DIMMER_H_
 
+#include <memory>
+
 #include "ash/ash_export.h"
 #include "base/macros.h"
 #include "ui/aura/window_observer.h"
 
 namespace ash {
 
-class WmWindow;
-
 // WindowDimmer creates a window whose opacity is animated by way of
 // SetDimOpacity() and whose size matches that of its parent. WindowDimmer is
 // intended to be used in cases where a certain set of windows need to appear
@@ -20,19 +20,18 @@ class WmWindow;
 // opacity, and then stacking window() above the windows that are to appear
 // obscured. The window created by WindowDimmer is owned by the parent, but also
 // deleted if WindowDimmer is deleted. It is expected that WindowDimmer is
-// deleted when the parent window is deleted (such as happens with
-// WmWindowUserData).
+// deleted when the parent window is deleted.
 class ASH_EXPORT WindowDimmer : public aura::WindowObserver {
  public:
   // Creates a new WindowDimmer. The window() created by WindowDimmer is added
   // to |parent| and stacked above all other child windows.
-  explicit WindowDimmer(WmWindow* parent);
+  explicit WindowDimmer(aura::Window* parent);
   ~WindowDimmer() override;
 
   void SetDimOpacity(float target_opacity);
 
-  WmWindow* parent() { return parent_; }
-  WmWindow* window() { return window_; }
+  aura::Window* parent() { return parent_; }
+  aura::Window* window() { return window_.get(); }
 
   // NOTE: WindowDimmer is an observer for both |parent_| and |window_|.
   // aura::WindowObserver:
@@ -43,8 +42,10 @@ class ASH_EXPORT WindowDimmer : public aura::WindowObserver {
   void OnWindowHierarchyChanging(const HierarchyChangeParams& params) override;
 
  private:
-  WmWindow* parent_;
-  WmWindow* window_;
+  aura::Window* parent_;
+
+  // See class description for details on ownership.
+  std::unique_ptr<aura::Window> window_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowDimmer);
 };