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

ui/base/events/event_dispatcher.cc

Index: ui/base/events/event_dispatcher.cc
diff --git a/ui/base/events/event_dispatcher.cc b/ui/base/events/event_dispatcher.cc
index 188523d4cfebb8d28f6059d5c50962e42fa4861a..1be042172d164e55db8e7d91abde064215ba2fcc 100644
--- a/ui/base/events/event_dispatcher.cc
+++ b/ui/base/events/event_dispatcher.cc
@@ -19,9 +19,9 @@ EventDispatcher::~EventDispatcher() {
 ////////////////////////////////////////////////////////////////////////////////
 // EventDispatcher, private:
 
-EventResult EventDispatcher::DispatchEventToSingleHandler(EventHandler* handler,
+void EventDispatcher::DispatchEventToSingleHandler(EventHandler* handler,
                                                           Event* event) {
-  return handler->OnEvent(event);
+  handler->OnEvent(event);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -29,6 +29,7 @@ EventResult EventDispatcher::DispatchEventToSingleHandler(EventHandler* handler,
 
 EventDispatcher::ScopedDispatchHelper::ScopedDispatchHelper(Event* event)
     : Event::DispatcherApi(event) {
+  set_result(ui::ER_UNHANDLED);
 }
 
 EventDispatcher::ScopedDispatchHelper::~ScopedDispatchHelper() {