Don't assume inline continuation's share repaint containers

Continuations aren't guaranteed to share a repaint container.
Teach the focus rect code to not cross repaint container bounds
to generate focus rects in the case of continuations, but
instead allow the subsequent repaint containers to handle their
own rects.

BUG=377536

Review URL: https://codereview.chromium.org/301763002

git-svn-id: svn://svn.chromium.org/blink/trunk@174912 bbb929c8-8fbe-4397-9dbb-9b2b20218538