Makes closing a fullscreen window refocus the window it came from.

ui/aura/window_tracker.h

Index: ui/aura/window_tracker.h
diff --git a/ui/aura/window_tracker.h b/ui/aura/window_tracker.h
index c11ac4b3d8f82778ac2a3e4bb1573b4f7680cdf0..960549a047405024ac10d8be18a1b42425ecda5a 100644
--- a/ui/aura/window_tracker.h
+++ b/ui/aura/window_tracker.h
@@ -18,9 +18,14 @@ namespace aura {
 // explicitly by Remove(), or implicitly when the window is destroyed.
 class AURA_EXPORT WindowTracker : public WindowObserver {
  public:
+  typedef std::set<Window*> Windows;
+
   WindowTracker();
   virtual ~WindowTracker();
 
+  // Returns the set of windows being observed.
+  const std::set<Window*>& windows() const { return windows_; }
+
   // Adds |window| to the set of Windows being tracked.
   void Add(Window* window);
 
@@ -35,8 +40,6 @@ class AURA_EXPORT WindowTracker : public WindowObserver {
   virtual void OnWindowDestroying(Window* window) OVERRIDE;
 
  private:
-  typedef std::set<Window*> Windows;
-
   Windows windows_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTracker);