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

ash/wm/overview/window_selector_window.h

Index: ash/wm/overview/window_selector_window.h
diff --git a/ash/wm/overview/window_selector_window.h b/ash/wm/overview/window_selector_window.h
index ef912ebdf806bb0f89bdf135d45ccc851c5815f2..fb49a58228a03209fe85d51f8e203c1d7883eaf5 100644
--- a/ash/wm/overview/window_selector_window.h
+++ b/ash/wm/overview/window_selector_window.h
@@ -11,7 +11,6 @@
 #include "ui/gfx/rect.h"
 
 namespace aura {
-class RootWindow;
 class Window;
 }
 
@@ -25,14 +24,14 @@ class WindowSelectorWindow : public WindowSelectorItem {
   virtual ~WindowSelectorWindow();
 
   // 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;