The output is only shown when it's failing. It makes the presubmit check much cleaner.
Also rename TestDescription and TestContent that were ill named.

TEST=none
BUG=none
Review URL: http://codereview.chromium.org/118415

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@18055 0039d316-1c4b-4281-b951-d872f2087c98