mochitest for bug 835044

--HG--
extra : transplant_source : %10Q%89%3F%ED%CA%BB%10/%98W%ED%7F%1F%E6%E9KM%D9%D6
b=835044 handle popup windows with parents in GetWidgetOffset r=tn

level="parent" popup windows can sometimes return a non-null parent, which is
their owner window, but their bounds are relative to the screen (previously
assumed to be the owner window origin).

--HG--
extra : transplant_source : %AEr%1F%1E%CC%08%A1%19%97%DBo%00f%5E%3EM%23R%FE%95
b=994351 break playing/seeked cycle in test

The seek is also moved to after the timeout to make the assertion failure
more reliable (in broken builds).

--HG--
extra : transplant_source : %CB_q%E3%CF%D9%25%85U%D3%B2X%CA%82%01%0D%91%D9%3C%A5
b=994351 re-enable media-element-source-seek-1 on B2G

--HG--
extra : transplant_source : %8E%A7%8A%CA%27%A6%FF%AD%B1S%86%E3u%CAL%C7%F26%D0%11