[pointerevents-tests] Pointercancel test fixes/clarifications (#1138)

Ran into these issues while working on https://bugzilla.mozilla.org/show_bug.cgi?id=1036985

View on GitHub: https://github.com/w3c/web-platform-tests/pull/1138

Received on Friday, 1 August 2014 19:56:55 UTC