Set the correct pressure for pointer events based on force

third_party/WebKit/public/platform/WebPointerProperties.h

 // Copyright (c) 2015 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.
 
 #ifndef WebPointerProperties_h
 #define WebPointerProperties_h
 
+#include <limits>
+
 namespace blink {
 
 // This class encapsulates the properties that are common between mouse and
 // pointer events and touch points as we transition towards the unified pointer
 // event model.
 // TODO(e_hakkinen): Replace WebTouchEvent with WebPointerEvent, remove
 // WebTouchEvent and WebTouchPoint and merge this into WebPointerEvent.
 class WebPointerProperties {
 public:
     WebPointerProperties()
         : button(ButtonNone)
         , id(0)
-        , force(0.f)
+        , force(std::numeric_limits<float>::quiet_NaN())
         , tiltX(0)
         , tiltY(0)
         , pointerType(PointerType::Unknown)
     {
     }
 
     enum Button {
         ButtonNone = -1,
         ButtonLeft,
         ButtonMiddle,
         ButtonRight
     };
 
     enum class PointerType : int {
         Unknown,
         Mouse,
         Pen,
         Touch,
         LastEntry = Touch // Must be the last entry in the list
     };
 
     Button button;
 
     int id;
+
+    // The valid range is [0,1], with NaN meaning pressure is not supported by
+    // the input device.
     float force;
 
     // Tilt of a pen stylus from surface normal as plane angles in degrees,
     // Values lie in [-90,90]. A positive tiltX is to the right and a positive
     // tiltY is towards the user.
     int tiltX;
     int tiltY;
 
     PointerType pointerType;
 };
 
 } // namespace blink
 
 #endif