Testing for IndexedDB is in a bad spot:

1. The class dependencies are out of control so creating a unittest involves a lot of world building
2. Testing edge cases involves poking unsupported parts of the system that leave it in an often invalid state that requires manual cleanup
3. Parts are totally untested, especially at the IPC level

We need to create a mojo-level testing harness to fix all of this, as well as enabling faster development of new patchs, and psuedo-fuzzing on this level.