On "pointerup" event, "pressure" must be zero

[compulim]

Tested on Chrome 42 on Windows with mouse, and also Safari on iOS 8.2 on iPad. The "pointerup" event emit a PointerEvent of pressure 0.5, instead of 0.

When testing the same code under IE11 with mouse (with or without PEP), the "pointerup" event give pressure of 0.

[appsforartists]

Here are the relevant bugs against Chrome and against the spec:

• https://crbug.com/648777
• pointerup pressure should always be 0 w3c/pointerevents#146

As you can see from the following chart, PEP currently does the wrong thing on iOS but the right thing on desktop. (Here's the test.)

Platform	Browser	Pointer	pointerup pressure is 0	pointerup pressure is whatever the last pointermove recorded
Android	Chrome	touch		☑️
iOS	Safari via PEP	touch		☑️
Mac	Chrome	trackpad	☑️
Mac	Chrome	Wacom stylus	☑️
Mac	Chrome	Wacom touch		☑️ (always 1, spec says it should be .5)
Mac	Firefox	trackpad	☑️
Mac	Firefox	Wacom stylus	☑️
Mac	Firefox	Wacom touch	☑️
Mac	Safari via PEP	trackpad	☑️
Mac	Safari via PEP	Wacom stylus	☑️
Mac	Safari via PEP	Wacom touch	☑️
ChromeOS	Chrome	touch		☑️
ChromeOS	Chrome	trackpad	☑️
Windows	Chrome or Edge	touch		☑️
Windows	Chrome or Edge	trackpad	☑️
Windows	Chrome or Edge	stylus	☑️
Windows	Firefox	touch	☑️
Windows	Firefox	trackpad	☑️
Windows	Firefox	stylus	☑️

[appsforartists]

Chrome is fixing their behavior. When #313 lands, this will be consistent in every case I've seen (except for touch on Windows)! 🎉