Desktop Aura: Allow tab drags out of window.

ui/aura/root_window_observer.h

Index: ui/aura/root_window_observer.h
diff --git a/ui/aura/root_window_observer.h b/ui/aura/root_window_observer.h
index 31bd37f04e59e02e8115d98097f50ef866bac8d6..81dcad95f55ff40c2fbe4987396a3ca136f2a140 100644
--- a/ui/aura/root_window_observer.h
+++ b/ui/aura/root_window_observer.h
@@ -8,6 +8,7 @@
 #include "ui/aura/aura_export.h"
 
 namespace gfx {
+class Point;
 class Size;
 }
 
@@ -21,6 +22,10 @@ class AURA_EXPORT RootWindowObserver {
   virtual void OnRootWindowResized(const RootWindow* root,
                                    const gfx::Size& old_size) {}
 
+  // Invoked after the RootWindow has been moved on screen.
+  virtual void OnRootWindowMoved(const RootWindow* root,
+                                 const gfx::Point& new_origin) {}
+
   // Invoked when the native windowing system sends us a request to close our
   // window.
   virtual void OnRootWindowHostCloseRequested(const RootWindow* root) {}