A bunch more tests have been converted.

Tests remaining to be converted;
 * test-change-playback-rate.html - Position dependent on frame rate, need to override callback.
 * test-preset-timings.html - Draws on a canvas, no idea how to test.
 * test-start-time-iterations.html - Not all the animation stuff is being intercepted, so the moving forward/backward in time isn't working.
 * test-step.html - Another one which draws on canvas.