Stop infinite recursion when generating anonymous table boxes

Update the list of box types to expect directly inside (anonymous) table
boxes to include 'table-column' (in addition to 'table-column-group'
and 'table-caption'.)  This fixes the code that looks for an existing
anonymous table section to add a child to so that it doesn't accidentally
try to add the child to the same table box again recursively.

Also drop a couple of lines of code that had no effect in practice.

BUG=330651

Review URL: https://codereview.chromium.org/131993002

git-svn-id: svn://svn.chromium.org/blink/trunk@165216 bbb929c8-8fbe-4397-9dbb-9b2b20218538