Implemented smooth scrolling using xinput2 in X11.

ui/events/platform/x11/x11_event_source.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/platform/x11/x11_event_source.h"
 
 #include <X11/extensions/XInput2.h>
 #include <X11/X.h>
 #include <X11/Xlib.h>
 #include <X11/XKBlib.h>
@@ skipping 121 matching lines @@
   return action;
 }
 
 uint32_t X11EventSource::DispatchEvent(XEvent* xevent) {
   uint32_t action = PlatformEventSource::DispatchEvent(xevent);
   if (xevent->type == GenericEvent &&
       xevent->xgeneric.evtype == XI_HierarchyChanged) {
     ui::UpdateDeviceList();
     hotplug_event_handler_->OnHotplugEvent();
   }
+
+  if (xevent->type == EnterNotify &&
+      xevent->xcrossing.detail != NotifyInferior &&
+      xevent->xcrossing.mode != NotifyUngrab) {
+    // Clear stored scroll data
+    ui::DeviceDataManagerX11::GetInstance()->InvalidateScrollClasses();
+  }
   return action;
 }
 
 void X11EventSource::StopCurrentEventStream() {
   continue_stream_ = false;
 }
 
 void X11EventSource::OnDispatcherListChanged() {
   if (!hotplug_event_handler_) {
     hotplug_event_handler_.reset(new X11HotplugEventHandler());
     // Force the initial device query to have an update list of active devices.
     hotplug_event_handler_->OnHotplugEvent();
   }
 }
 
 }  // namespace ui