[css-tables] Set needsLayout on cells when column border width changes

When borders collapse, col/colgroup borders affect cell widths but we
weren't marking cells properly. As a result cells and tables were using
their old widths.

BUG=613728

Review-Url: https://codereview.chromium.org/2149953004
Cr-Commit-Position: refs/heads/master@{#405818}
6 files changed