Fix repaint rects from fast/repaint/window-resize tests

By observation, these tests are supposed to be printing out multiple
sets of repaint rects.  text-based-repaint doesn't handle multiple sets
of runRepaintTest, so for this unfortunately synchronous resize API,
just have it handle all the repaints itself.

This is also the only synchronous-requiring repaint test, so fixing
this makes it easier to make all repaint tests actually go through the
full asynchronous paint path.

BUG=361729

Review URL: https://codereview.chromium.org/277573003

git-svn-id: svn://svn.chromium.org/blink/trunk@173770 bbb929c8-8fbe-4397-9dbb-9b2b20218538