Add unit instrumentation tests for Chromoting Android code.

This adds a new GYP target for building Java unittests for Chromoting,
including a simple unittest example.

BUG=322095

Review URL: https://codereview.chromium.org/115953003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242060 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242060