We concatenate JSMs together so we use less compartments and therefore
less memory. This is intended to be a temporary hack until the overhead
of compartments is less.
We have introduced a new background service that captures session state
in preferences. Firefox Health Report now moves entries from preferences
to its database at payload generation time.
We've also introduced a few random APIs, such as enqueueTransaction()
and the ability for providers to have access to their own pref branch.
