[CSS Grid Layout] CSSParser should reject <track-list> without a <track-size>

The case of <track-list> without a <track-size> was properly handled
but that's because style resolution had to account for the parsing
being not totally right.

This refactoring will help with implementing parsing for
<repeat-function> as the code matches the specification more closely.

TEST=fast/css-grid-layout/named-grid-line-get-set.html

Review URL: https://chromiumcodereview.appspot.com/16917013

git-svn-id: svn://svn.chromium.org/blink/trunk@152914 bbb929c8-8fbe-4397-9dbb-9b2b20218538
4 files changed