Mojo: Make sample_test.cc a gtest (and re-enable it).

This also entails making it link with mojo_run_all_unittests, and
changing deps to allow a dependency on testing (hence gtest and
theoretically gmock).

R=darin@chromium.org, davemoore

Review URL: https://codereview.chromium.org/66103004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234336 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234336
Disable TextureLayerNoExtraCommitForMailboxTest because of crashes.

TBR=kloveless

BUG=317854

Review URL: https://codereview.chromium.org/69533002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234337 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234337