Currently CacheStorageDiskStore reads entire files into dirty memory. When many DOMCache operations in flight, this can lead to an temporary explosion in NetworkProcess memory usage (in the gigabytes of footprint).

To fix this issue, we should explore using read-only mapped files in CacheStorageDiskStore instead, as we do with the regular network cache. This trades dirty footprint for higher vnode usage. But presumably that's okay as the number of vnodes that would be consumed by DOMCache should be much lower than the number of vnodes used by NetworkCache.