[CSS Shapes] shape-outside layout incorrect when line spans rounded box rounded corners

The fix for this bug was included in https://codereview.chromium.org/124353002.  This is the regression test that should have been included with that patch.


BUG=331921

Review URL: https://codereview.chromium.org/98283006

git-svn-id: svn://svn.chromium.org/blink/trunk@164553 bbb929c8-8fbe-4397-9dbb-9b2b20218538