Fix results panel to not have a min-height for the list of failures.

If the list of failures is short enough, there's no need to take up
extra whitespace.

NOTRY=true

Review URL: https://codereview.chromium.org/412113002

git-svn-id: svn://svn.chromium.org/blink/trunk@178808 bbb929c8-8fbe-4397-9dbb-9b2b20218538