Shopify/liquid — pull request #191 by raggi (2013-05-14 14:53:31+00:00)
Title: Add a class cache to avoid runtime extend calls

* Strainer has a class cache that creates Strainer subclasses for each filter
set that is used on .create calls.
* Context now creates a list of filters and passes this to Strainer.create to
utilize the class cache in almost all use cases.
* If add_filter was called after a render, then the method cache may still be
invalidated.