events: Change gesture-event handler in EventHandler to not return any values.

ui/views/widget/native_widget_aura.cc

Index: ui/views/widget/native_widget_aura.cc
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index f0779c33a822ad96fff84e0cbc0ba4e657ab200d..0d804a6cf63e3726e053874af5c96d258fc3a3d6 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -841,9 +841,9 @@ ui::EventResult NativeWidgetAura::OnTouchEvent(ui::TouchEvent* event) {
   return delegate_->OnTouchEvent(event);
 }
 
-ui::EventResult NativeWidgetAura::OnGestureEvent(ui::GestureEvent* event) {
+void NativeWidgetAura::OnGestureEvent(ui::GestureEvent* event) {
   DCHECK(window_->IsVisible());
-  return delegate_->OnGestureEvent(event);
+  delegate_->OnGestureEvent(event);
 }
 
 ////////////////////////////////////////////////////////////////////////////////