Test that Audio() sets 'autobuffer' attribute.

RUN(media = new Audio())

++ Test initial attribute value
EXPECTED (media.getAttribute('autobuffer') != 'null') OK
EXPECTED (media.autobuffer == 'true') OK

RUN(media.src = 'content/test.wav')
RUN(media.load())

++ Test after 'load' event
EXPECTED (media.getAttribute('autobuffer') != 'null') OK
EXPECTED (media.autobuffer == 'true') OK
END OF TEST

