Tests AudioBufferSourceNode start() with a variety of offsets and durations.

On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".

PASS start(when): implicitly play whole buffer from beginning to end
PASS start(when, 0): play whole buffer from beginning to end explicitly giving offset of 0
PASS start(when, 0, 8_frames): play whole buffer from beginning to end explicitly giving offset of 0 and duration of 8 frames
PASS start(when, 4_frames): play with explicit non-zero offset
PASS start(when, 4_frames, 4_frames): play with explicit non-zero offset and duration