Changed DeviceDataManagerX11 to use xinput1 for low resolution scroll devices

ui/events/devices/x11/device_data_manager_x11.cc

Index: ui/events/devices/x11/device_data_manager_x11.cc
diff --git a/ui/events/devices/x11/device_data_manager_x11.cc b/ui/events/devices/x11/device_data_manager_x11.cc
index 9d83afe1e34c98dbdaa8e91337c4b4818b295d6e..580e7dd9fc13d42e2fddbe37df985c565df6fa4e 100644
--- a/ui/events/devices/x11/device_data_manager_x11.cc
+++ b/ui/events/devices/x11/device_data_manager_x11.cc
@@ -771,6 +771,16 @@ void DeviceDataManagerX11::UpdateScrollClassDevice(
     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 that.

[sadrul, 2016/04/22 02:42:23]

s/then use that/then use the xinput1 resolution instead/

[Will Shackleton, 2016/04/22 14:56:55]

Done.

+  if (legacy_scroll_available &&
+      std::abs(scroll_class_info->increment) <= 1.0) {
+    return;

[sadrul, 2016/04/22 02:42:22]

Does this need to reset some state of |info|?

[Will Shackleton, 2016/04/22 14:56:55]

No - the |info| fields are reset upon call to this method---it's only ever
called to fill the |info| object in from a clean state.

+  }
+
   switch (scroll_class_info->scroll_type) {
     case XIScrollTypeVertical:
       info.vertical.number = scroll_class_info->number;