Desktop Aura: Allow tab drags out of window.

ui/aura/root_window.h

Index: ui/aura/root_window.h
diff --git a/ui/aura/root_window.h b/ui/aura/root_window.h
index 92362690b39b4c988efe115f07795c13ff63eed3..9f4b9f1fa3a823eb9fd66f1aec9e8506d0dc836e 100644
--- a/ui/aura/root_window.h
+++ b/ui/aura/root_window.h
@@ -109,6 +109,9 @@ class AURA_EXPORT RootWindow : public ui::CompositorDelegate,
   // Shows the root window host.
   void ShowRootWindow();
 
+  // Hides the root window host.
+  void HideRootWindow();
+
   RootWindowHostDelegate* AsRootWindowHostDelegate();
 
   // Sets the size of the root window.
@@ -304,6 +307,7 @@ class AURA_EXPORT RootWindow : public ui::CompositorDelegate,
   virtual bool OnHostTouchEvent(ui::TouchEvent* event) OVERRIDE;
   virtual void OnHostLostCapture() OVERRIDE;
   virtual void OnHostPaint() OVERRIDE;
+  virtual void OnHostMoved(const gfx::Point& origin) OVERRIDE;
   virtual void OnHostResized(const gfx::Size& size) OVERRIDE;
   virtual float GetDeviceScaleFactor() OVERRIDE;
   virtual RootWindow* AsRootWindow() OVERRIDE;