events: Start changing EventHandler interface to not return a value.

ui/views/corewm/activation_change_shim.cc

Index: ui/views/corewm/activation_change_shim.cc
diff --git a/ui/views/corewm/activation_change_shim.cc b/ui/views/corewm/activation_change_shim.cc
index 6184606055900ee00531584cd5e6b77e98d90d5f..f1822914beee493c5fd390baf9bf9cc99ff0d34c 100644
--- a/ui/views/corewm/activation_change_shim.cc
+++ b/ui/views/corewm/activation_change_shim.cc
@@ -34,14 +34,14 @@ void ActivationChangeShim::OnWindowActivated(aura::Window* active,
                                              aura::Window* old_active) {
 }
 
-ui::EventResult ActivationChangeShim::OnEvent(ui::Event* event) {
+void ActivationChangeShim::OnEvent(ui::Event* event) {
   if (event->type() == FocusChangeEvent::activation_changed_event_type()) {
     DCHECK(UseFocusController());
     FocusChangeEvent* fce = static_cast<FocusChangeEvent*>(event);
     OnWindowActivated(static_cast<aura::Window*>(event->target()),
                       static_cast<aura::Window*>(fce->last_focus()));
   }
-  return EventHandler::OnEvent(event);
+  EventHandler::OnEvent(event);
 }
 
 }  // namespace corewm