This bug covers the work to extend the test functionality delivered in bug 1309394 to include running of native code in content. Bug 1309394 added some simple tests that use js-ctypes to make OS library/system calls from the content process. The tests validate whether or not operations are allowed or blocked in the content sandbox. The work here is to extend the tests to use js-ctypes to load a per-platform library which runs tests written in compiled code. There is some additional value in having native tests in addition to JS tests: 1) In some cases it's easier to test new functionality using native code compared to having to use js-ctypes exclusively; 2) native tests would be easier to convert to gtests if we need to do that in the future. See discussion on 1309394; and 3) browser bugs could prevent JS tests from working while native calls might still work.