Add very simple test list for chromium_trybot recipe to the chromium tree

This will allow changing, adding, and removing tests without two-sided
patches.

The list format can be extended in the future, for now keeping it as simple
and static as possible.

BUG=332239
R=darin@chromium.org, iannucci@chromium.org

Review URL: https://codereview.chromium.org/166663004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252050 0039d316-1c4b-4281-b951-d872f2087c98

testing/buildbot/OWNERS

+darin@chromium.org
+phajdan.jr@chromium.org
+sky@chromium.org

testing/buildbot/chromium_trybot.json

+[
+  "mojo_common_unittests",
+  "mojo_js_unittests",
+  "mojo_public_bindings_unittests",
+  "mojo_public_environment_unittests",
+  "mojo_public_system_unittests",
+  "mojo_public_utility_unittests",
+  "mojo_shell_unittests",
+  "mojo_system_unittests"
+]