Mojo: Fix perf tests.

test_support_perf has its own main() (i.e., in run_all_perftests.cc), which
obviously doesn't initialize Mojo. Oops.

R=darin@chromium.org, davemoore@chromium.org

Review URL: https://codereview.chromium.org/89373002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237429 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237429