Layout captions in simplifiedNormalFlowLayout for tables.

      It is currently possible to get into simplifiedNormalFlowLayout for a table
while the captions need layout. Currently the simplified code will just
iterate over all of the table sections and lay them out if needed.

This CL adds iteration over the table captions as well and makes sure they're
also laid out during simplifedNormalFlowLayout.

BUG=414109

Review URL: https://codereview.chromium.org/804383002

git-svn-id: svn://svn.chromium.org/blink/trunk@187509 bbb929c8-8fbe-4397-9dbb-9b2b20218538