Using JSON.stringify on an object containing an asset's source was pretty slow.
Concatenating the source with the useSourceMaps variable still produces a
unique string, and is many times faster.
Coverage decreased (-0.5%) to 69.63% when pulling ec67b2ecba65a954d4e15c88f4c176ba51a3487a on faster-cache-key into 3edc9251f5152e16dcd97be63dab563ac69f9de8 on master.
Using JSON.stringify on an object containing an asset's source was pretty slow. Concatenating the source with the useSourceMaps variable still produces a unique string, and is many times faster.