Make sure that the pressure is always 0 for pointerup events

ui/events/x/events_x_utils.cc

 // Copyright (c) 2016 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/x/events_x_utils.h"
 
 #include <stddef.h>
 #include <string.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
@@ skipping 707 matching lines @@
   return radius;
 }
 
 float GetTouchAngleFromXEvent(const XEvent& xev) {
   return GetTouchParamFromXEvent(
              xev, ui::DeviceDataManagerX11::DT_TOUCH_ORIENTATION, 0.0) /
          2.0;
 }
 
 float GetTouchForceFromXEvent(const XEvent& xev) {
   double force = 0.0;

[sadrul, 2017/02/21 19:18:07]

Wrap everything below in a 'if (event->evtype != TouchEnd)' check

   force = GetTouchParamFromXEvent(
       xev, ui::DeviceDataManagerX11::DT_TOUCH_PRESSURE, 0.0);
   unsigned int deviceid =
       static_cast<XIDeviceEvent*>(xev.xcookie.data)->sourceid;
   // Force is normalized to fall into [0, 1]
   if (!ui::DeviceDataManagerX11::GetInstance()->NormalizeData(
           deviceid, ui::DeviceDataManagerX11::DT_TOUCH_PRESSURE, &force))
     force = 0.0;
+  XIDeviceEvent* event = static_cast<XIDeviceEvent*>(xev.xcookie.data);
+  if (event->evtype == XI_TouchEnd)
+    force = 0.0;
   return force;
 }
 
 bool GetScrollOffsetsFromXEvent(const XEvent& xev,
                                 float* x_offset,
                                 float* y_offset,
                                 float* x_offset_ordinal,
                                 float* y_offset_ordinal,
                                 int* finger_count) {
   if (DeviceDataManagerX11::GetInstance()->IsScrollEvent(xev)) {
@@ skipping 59 matching lines @@
 }
 
 void ResetTimestampRolloverCountersForTesting(
     std::unique_ptr<base::TickClock> tick_clock) {
   g_last_seen_timestamp_ms = 0;
   g_rollover_ms = 0;
   SetEventTickClockForTesting(std::move(tick_clock));
 }
 
 }  // namespace ui