Changed DeviceDataManagerX11 to use xinput1 for low resolution scroll devices

ui/events/devices/x11/device_data_manager_x11.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/devices/x11/device_data_manager_x11.h"
 
 #include <stddef.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xlib.h>
@@ skipping 755 matching lines @@
   valuator_min_[deviceid][data_type] = valuator_class_info->min;
   valuator_max_[deviceid][data_type] = valuator_class_info->max;
   return IsCMTDataType(data_type);
 }
 
 void DeviceDataManagerX11::UpdateScrollClassDevice(
     XIScrollClassInfo* scroll_class_info,
     int deviceid) {
   DCHECK(deviceid >= 0 && deviceid < kMaxDeviceNum);
   ScrollInfo& info = scroll_data_[deviceid];
+
+  bool legacy_scroll_available =
+      (scroll_class_info->flags & XIScrollFlagNoEmulation) == 0;
+  // If the device's highest resolution is lower than the resolution of xinput1
+  // then use xinput1's events instead (ie. don't configure smooth scrolling).
+  if (legacy_scroll_available &&
+      std::abs(scroll_class_info->increment) <= 1.0) {
+    return;
+  }
+
   switch (scroll_class_info->scroll_type) {
     case XIScrollTypeVertical:
       info.vertical.number = scroll_class_info->number;
       info.vertical.increment = scroll_class_info->increment;
       info.vertical.position = 0;
       info.vertical.seen = false;
       break;
     case XIScrollTypeHorizontal:
       info.horizontal.number = scroll_class_info->number;
       info.horizontal.increment = scroll_class_info->increment;
@@ skipping 88 matching lines @@
     } else {
       keyboards.erase(it);
       ++blocked_iter;
     }
   }
   // Notify base class of updated list.
   DeviceDataManager::OnKeyboardDevicesUpdated(keyboards);
 }
 
 }  // namespace ui