[cairo] Adventures in caching

[Mike Emmel]

Whats wrong with adding the concept of a weak reference for caching.
The weak reference since its basically a boolean could be bumped each
time a cache object goes strong counting the number of times it was
strongly referenced allowing you to decide to either expand the cache
if most objects were strongly referenced often or drop the ones that
never or seldom went strong or some other more complex algo.

Mike