events: Update scroll and touch handlers to not return EventResult.

ash/wm/user_activity_detector.cc

Index: ash/wm/user_activity_detector.cc
diff --git a/ash/wm/user_activity_detector.cc b/ash/wm/user_activity_detector.cc
index ee6a2b7e7355738c8e12c702049e085d8e9cf6b4..4338accbe294a124bca9a197b6d59ca7273180c9 100644
--- a/ash/wm/user_activity_detector.cc
+++ b/ash/wm/user_activity_detector.cc
@@ -48,14 +48,12 @@ ui::EventResult UserActivityDetector::OnMouseEvent(ui::MouseEvent* event) {
   return ui::ER_UNHANDLED;
 }
 
-ui::EventResult UserActivityDetector::OnScrollEvent(ui::ScrollEvent* event) {
+void UserActivityDetector::OnScrollEvent(ui::ScrollEvent* event) {
   MaybeNotify();
-  return ui::ER_UNHANDLED;
 }
 
-ui::EventResult UserActivityDetector::OnTouchEvent(ui::TouchEvent* event) {
+void UserActivityDetector::OnTouchEvent(ui::TouchEvent* event) {
   MaybeNotify();
-  return ui::ER_UNHANDLED;
 }
 
 void UserActivityDetector::OnGestureEvent(ui::GestureEvent* event) {