These steps are the best definition we have for how the ready state
should be set, and it seems to be reasonable to apply to plain file
playback as well.
Since our file demuxers are hardcoded to return the entire duration as
buffered, the ready state immediately progresses to HAVE_CURRENT_DATA.
This will probably change once we can check the demuxers for buffered
data.
Since we know whether we're buffering from the PlaybackManager state,
let's use that to update the ready state. This ensures that when we set
the ready state to HAVE_CURRENT_DATA, we actually have a frame.
Setting the ready state to HAVE_ENOUGH_DATA should probably still be
further conditioned on the buffer size in IncrementallyPopulatedStream,
but this is still an improvement for now.
This test will try to load an invalid src, then in the error handler,
set the src to a valid URL. In the process, any events that should have
deterministic ordering will be logged to compare to the expectation.
