Make GetRootWindow() return a Window instead of a RootWindow.

ash/wm/overview/window_selector_panels.h

Index: ash/wm/overview/window_selector_panels.h
diff --git a/ash/wm/overview/window_selector_panels.h b/ash/wm/overview/window_selector_panels.h
index 785c6dce83058d87143fbdcc0865c2214d759010..bcc9137004c8b26bc341f87a12341fb62b8c6c25 100644
--- a/ash/wm/overview/window_selector_panels.h
+++ b/ash/wm/overview/window_selector_panels.h
@@ -10,11 +10,6 @@
 #include "base/memory/scoped_vector.h"
 #include "ui/gfx/rect.h"
 
-namespace aura {
-class RootWindow;
-class Window;
-}
-
 namespace ash {
 
 class ScopedTransformOverviewWindow;
@@ -32,14 +27,14 @@ class WindowSelectorPanels : public WindowSelectorItem {
   void AddWindow(aura::Window* window);
 
   // WindowSelectorItem:
-  virtual aura::RootWindow* GetRootWindow() OVERRIDE;
+  virtual aura::Window* GetRootWindow() OVERRIDE;
   virtual aura::Window* TargetedWindow(const aura::Window* target) OVERRIDE;
   virtual void RestoreWindowOnExit(aura::Window* window) OVERRIDE;
   virtual aura::Window* SelectionWindow() OVERRIDE;
   virtual void RemoveWindow(const aura::Window* window) OVERRIDE;
   virtual bool empty() const OVERRIDE;
   virtual void PrepareForOverview() OVERRIDE;
-  virtual void SetItemBounds(aura::RootWindow* root_window,
+  virtual void SetItemBounds(aura::Window* root_window,
                              const gfx::Rect& target_bounds,
                              bool animate) OVERRIDE;