Shopify/shopify_app — pull request #105 by Hammadk (2014-11-04 21:34:06+00:00)
Title: Memoize shop_session in LoginProtection

#### Problem:
`ShopifySessionRepository.retrieve` can be pretty expensive if it requires fetching items from the database.

#### Solution:
Memoize the results of `shop_session` instance method.

@csaunders @awd please review.
cc: @nickhoffman @mtaher