Use begin/end istead of first/last for rule ranges.

MatchResult used -1 for empty ranges of matched properties. Use begin/end
instead where begin == end means we have an empty range.

As requested in https://codereview.chromium.org/1155393002/

R=timloh@chromium.org

Review URL: https://codereview.chromium.org/1162583002

git-svn-id: svn://svn.chromium.org/blink/trunk@196065 bbb929c8-8fbe-4397-9dbb-9b2b20218538
4 files changed