Adds mojo_view_manager_unittests to some linux bots

I enabled these tests on the fyi waterfall a couple of days and back
and they look pretty stable.

BUG=none
TEST=none
R=yzshenchromium.org

Review URL: https://codereview.chromium.org/271443005

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@269192 4ff67af0-8c30-449e-8e8b-ad334ec8d88c