The pickle jar contains old pickles of objects that we want to ensure work in the future. For example, if you made the changes at 9907 as the are, then possibly many pickles out in the wild would break. Instead of trying to update the pickle jar, the appropriate thing to do would be to add the following to sage/plot/misc.py
#For backward compatibility -- see #9907.

That way, the old pickles will still work as they will still be able to find the decorators in sage.plot.misc.