Andrew Nicols 9626e56812 MDL-64835 JS: Reduce cache invalidation checks
The cache invalidation check was previously occuring every time either
the `set` or `get` function was called on the cache. However, the cache
invalidation check is based on the jsrev which is static for the
lifetime of the page.

This change moved the invalidation to happen during the setup of the AMD
module such that it only happens one time per storage type (Local +
Session).
2019-02-13 10:13:05 +08:00
..