Two changes to desktop aura for tooltips:

ui/aura/test/event_generator.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_AURA_TEST_EVENT_GENERATOR_H_
 #define UI_AURA_TEST_EVENT_GENERATOR_H_
 
 #include <list>
 #include <vector>
 
@@ skipping 117 matching lines @@
 
   // Generates a double click event using the left button.
   void DoubleClickLeftButton();
 
   // Generates a right button press event.
   void PressRightButton();
 
   // 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);
   void MoveMouseToInHost(int x, int y) {
     MoveMouseToInHost(gfx::Point(x, y));
   }
 
   // Generates events to move mouse to be the given |point| in screen
   // coordinates.
   void MoveMouseTo(const gfx::Point& point_in_screen, int count);
@@ skipping 163 matching lines @@
   // Set to true to cause events to be posted asynchronously.
   bool async_;
 
   DISALLOW_COPY_AND_ASSIGN(EventGenerator);
 };
 
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_EVENT_GENERATOR_H_