Make it easier to parse the output assertion

Currently, when the list of outputs doesn't match the expected outputs,
grit just prints a big unreadable block of text. This change just makes
it much easier to parse that output and fix the offending expectations.

Review URL: https://codereview.chromium.org/576613002/
Patch from Chris Hopman <cjhopman@chromium.org>!


git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@177 7262f16d-afe8-6277-6482-052fa10e57b1