This avoids the need for every class using this rule to call
injectMembers manually, and even for SchemaUpgradeTestEnvironment to
expose its Injector and ReviewDb instances.
Ultimately this means simple schema upgrade tests don't need to write
@Before methods, and the only line of boilerplate required for a test
to be a schema upgrade test is defining the @Rule. This minimal
boilerplate avoids the temptation to extract an abstract test class as
in I733e211e.
Change-Id: I4a0e9d3a885b9709c25cd7cddb6430924a66d5af
47b2ee03fa