Update layout tests to use floats for touch point locations.

plugins/touch-events-details.html and plugins/transformed-events.html
started to fail when touch point locations became floating point.

This patch fixes that. This depends on
https://codereview.chromium.org/210083002/.

BUG=354787

Review URL: https://codereview.chromium.org/210093002

git-svn-id: svn://svn.chromium.org/blink/trunk@170179 bbb929c8-8fbe-4397-9dbb-9b2b20218538