Autofill: Fix GuardedBy false-positives in Session.

Warnings are due to inner class fields being guarded by an outer
class lock. It's actually safe because the inner class instance is
only ever assigned to a final field in the outer class.

Test: builds
Bug: 210926084
Change-Id: Ia5258ecf2fd01bcb951692626a616a7a51d63fab
1 file changed