[css-grid] Fix referencing name of 1st line followed by auto repeat()

When referencing a line name in the grid-placement properties, if the
first track was defined using the auto repeat() syntax, then the code
would assume that the line had to appear after the repeated tracks.

However, it can precede them, e.g.
    grid-template-columns: [first] repeat(auto-fill, 10px)

This patch fixes this by removing the special casing for auto repeat()
being the first tracks.

BUG=966090

TEST=external/wpt/css/css-grid/placement/grid-placement-using-named-grid-lines-002.html

Change-Id: Ic9c1199532f8ed06c958b80aef4580b7a318490c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2071873
Reviewed-by: Javier Fernandez <jfernandez@igalia.com>
Commit-Queue: Oriol Brufau <obrufau@igalia.com>
Cr-Commit-Position: refs/heads/master@{#744426}
2 files changed