Fix and clean up parsing for counter-reset and counter-increment

We currently incorrectly accept values like 'c 20 30' in parsing of
counter-reset and counter-increment since we fail to check the stream
has finished.

Of the values in the added test, Chrome incorrectly allows accept
'c 10 20' and 'hello "hello"', Firefox and Opera 12 accept none
of the values, and IE 11 accepts 'hello "hello"'m 'c 10 20' and
'c + 5' incorrectly.

BUG=404023

Review URL: https://codereview.chromium.org/475503006

git-svn-id: svn://svn.chromium.org/blink/trunk@181165 bbb929c8-8fbe-4397-9dbb-9b2b20218538