nsIMicrosummary in Firefox 3.5

 Add a microsummary observer to this microsummary.

 @param observer
        the microsummary observer to add

 Microsummary equivalence test
 Microsummaries equal if they summarize the same page with the same
 microsummary-generator (see also nsIMicrosummaryGenerator::equals).

 Note: this method returns false if either objects don't have a generator

 Remove a microsummary observer from this microsummary.

 @param observer
        the microsummary observer to remove

 Update the microsummary, first loading its generator and page content
 as necessary.  If you want know when a microsummary finishes updating,
 add an observer before calling this method.