Ignoring math expressions involving percentages for widths and heights
on table elements

According to the standard, math expressions involving percentages for
widths and heights on table elements have to be treated as if "auto"
had been specified. The patch implements this fallback.

BUG=350852

Review URL: https://codereview.chromium.org/192603003

git-svn-id: svn://svn.chromium.org/blink/trunk@176946 bbb929c8-8fbe-4397-9dbb-9b2b20218538