Two changes to desktop aura for tooltips:

ui/aura/test/event_generator.cc

 // 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.
 
 #include "ui/aura/test/event_generator.h"
 
 #include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "ui/aura/client/screen_position_client.h"
@@ skipping 127 matching lines @@
 }
 
 void EventGenerator::PressRightButton() {
   PressButton(ui::EF_RIGHT_MOUSE_BUTTON);
 }
 
 void EventGenerator::ReleaseRightButton() {
   ReleaseButton(ui::EF_RIGHT_MOUSE_BUTTON);
 }
 
+void EventGenerator::SendMouseExit() {
+  gfx::Point exit_location(current_location_);
+  ConvertPointToTarget(current_root_window_, &exit_location);
+  ui::MouseEvent mouseev(ui::ET_MOUSE_EXITED, exit_location, exit_location,
+                         flags_);
+  Dispatch(&mouseev);
+}
+
 void EventGenerator::MoveMouseToInHost(const gfx::Point& point_in_host) {
   const ui::EventType event_type = (flags_ & ui::EF_LEFT_MOUSE_BUTTON) ?
       ui::ET_MOUSE_DRAGGED : ui::ET_MOUSE_MOVED;
   ui::MouseEvent mouseev(event_type, point_in_host, point_in_host, flags_);
   Dispatch(&mouseev);
 
   current_location_ = point_in_host;
   current_root_window_->ConvertPointFromHost(&current_location_);
 }
 
@@ skipping 406 matching lines @@
     base::MessageLoopProxy::current()->PostTask(
         FROM_HERE,
         base::Bind(&EventGenerator::DispatchNextPendingEvent,
                    base::Unretained(this)));
   }
 }
 
 
 }  // namespace test
 }  // namespace aura