Desktop Aura: Allow tab drags out of window.

ui/views/widget/widget.h

Index: ui/views/widget/widget.h
diff --git a/ui/views/widget/widget.h b/ui/views/widget/widget.h
index 490fa9acc2c22918d097d849de50aa15457ac23c..84ed582859ae70664fb08d86a08258cd28f625b9 100644
--- a/ui/views/widget/widget.h
+++ b/ui/views/widget/widget.h
@@ -319,8 +319,10 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
 
   // Starts a nested message loop that moves the window. This can be used to
   // start a window move operation from a mouse moved event. This returns when
-  // the move completes.
-  MoveLoopResult RunMoveLoop();
+  // the move completes. |drag_offset| is the offset from the top left corner
+  // of the window to the point where the cursor is dragging, and is used to
+  // offset the bounds of the window from the cursor.
+  MoveLoopResult RunMoveLoop(const gfx::Point& drag_offset);
 
   // Stops a previously started move loop. This is not immediate.
   void EndMoveLoop();