Add filter for playback rates.

@valera-rozuvan please, review.

Because of problems with muting sound outside of range 0.25 and 5.0, we should filter our available playback rates.
Issues:
   https://code.google.com/p/chromium/issues/detail?id=264341
   https://bugzilla.mozilla.org/show_bug.cgi?id=840745
   https://developer.mozilla.org/en-US/docs/DOM/HTMLMediaElement