Two changes to desktop aura for tooltips:

ui/aura/test/event_generator.h

Index: ui/aura/test/event_generator.h
diff --git a/ui/aura/test/event_generator.h b/ui/aura/test/event_generator.h
index a4ffca76c3cf0f6e9fae0af898e05046ed8ccd6e..511dd777e909124588c31325b2974df83958add6 100644
--- a/ui/aura/test/event_generator.h
+++ b/ui/aura/test/event_generator.h
@@ -135,6 +135,9 @@ class EventGenerator {
   // Generates a right button release event.
   void ReleaseRightButton();
 
+  // Generates a mouse exit.
+  void SendMouseExit();
+
   // Generates events to move mouse to be the given |point| in the
   // |current_root_window_|'s host window coordinates.
   void MoveMouseToInHost(const gfx::Point& point_in_host);