Make ComboboxListener work around being deleted from OnSelectedIndexChanged().

ui/views/controls/combobox/combobox.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/views/controls/combobox/combobox.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "grit/ui_resources.h"
 #include "ui/base/accessibility/accessible_view_state.h"
@@ skipping 450 matching lines @@
   dropdown_open_ = false;
   closed_time_ = base::Time::Now();
 
   // Need to explicitly clear mouse handler so that events get sent
   // properly after the menu finishes running. If we don't do this, then
   // the first click to other parts of the UI is eaten.
   SetMouseHandler(NULL);
 }
 
 void Combobox::OnSelectionChanged() {
+  NotifyAccessibilityEvent(ui::AccessibilityTypes::EVENT_VALUE_CHANGED, false);
+  SchedulePaint();
   if (listener_)
     listener_->OnSelectedIndexChanged(this);
-  NotifyAccessibilityEvent(ui::AccessibilityTypes::EVENT_VALUE_CHANGED, false);
-  SchedulePaint();
+  // |this| may now be deleted.
 }
 
 int Combobox::MenuCommandToIndex(int menu_command_id) const {
   // (note that the id received is offset by kFirstMenuItemId)
   // Revert menu ID offset to map back to combobox model.
   int index = menu_command_id - kFirstMenuItemId;
   DCHECK_LT(index, model()->GetItemCount());
   return index;
 }
 
 }  // namespace views