Mojo: Remove some base/ dependencies from mojo/public/tests/.

mojo/public/tests/ shouldn't depend on stuff outside of public/.

(Still left to do: a couple dependencies in test_support.cc.)

R=darin@chromium.org

Review URL: https://codereview.chromium.org/139843002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244966 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244966