DO NOT MERGE: SF: Fix a race between layer creation and apply transaction

Between commitCreatedLayers and applyTransactions in the main
thread, the client could create a new layer and queue a transaction.
This will mean a layer transaction can be applied before the layer
can be committed.

Fix this by flushing the transactions to be applied before
committing any new layers.

Test: presubmit
Fixes: b/262336014
Change-Id: I9987614ade29456453de3610782a645ea9db0892