When inserting a new line between a two-word misspelling (for example:
'It should be upper \ncase.') the spell checker checks only the first
part, leaving the second part marked. This patch corrects this behaviour
by running the spell checker on both lines.

BUG=173443

Review URL: https://codereview.chromium.org/256583003

git-svn-id: svn://svn.chromium.org/blink/trunk@177310 bbb929c8-8fbe-4397-9dbb-9b2b20218538