MediaSource, clipping buffer?

Question

JavaScript

Question for MediaSource (WebKit) connoisseurs: how can you clear / trim the buffer (returned by the addSourceBuffer method of the MediaSource component) to free memory as it plays (now it eats very well)?
Adding a second buffer throws QUOTA_EXCEEDED_ERR: DOM Exception 22, so you can't keep two buffers and change them.
the SourceBuffer interfaces seem to have remove, but the method is not implemented.
I would like to keep the continuity of playback.
Thanks in advance!