Revert of Remove enable/disable wheel gestures setting.

ui/events/blink/input_handler_proxy.cc

Index: ui/events/blink/input_handler_proxy.cc
diff --git a/ui/events/blink/input_handler_proxy.cc b/ui/events/blink/input_handler_proxy.cc
index 9b13d93cd2496cb88dec75fdb796d236368319a6..811554176974f8afdcfe2a08b02ea5c5bb685d9b 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -239,6 +239,7 @@
       has_fling_animation_started_(false),
       smooth_scroll_enabled_(false),
       uma_latency_reporting_enabled_(base::TimeTicks::IsHighResolution()),
+      use_gesture_events_for_mouse_wheel_(true),
       touch_start_result_(kEventDispositionUndefined) {
   DCHECK(client);
   input_handler_->BindToClient(this);
@@ -449,6 +450,7 @@
   if (!wheel_event.hasPreciseScrollingDeltas && fling_curve_)
     CancelCurrentFling();
 
+  if (use_gesture_events_for_mouse_wheel_) {
     cc::EventListenerProperties properties =
         input_handler_->GetEventListenerProperties(
             cc::EventListenerClass::kMouseWheel);
@@ -464,6 +466,8 @@
         NOTREACHED();
         return DROP_EVENT;
     }
+  }
+  return ScrollByMouseWheel(wheel_event);
 }
 
 InputHandlerProxy::EventDisposition InputHandlerProxy::ScrollByMouseWheel(