Reland CHECKs that verify bookmark USS invariants

Relands invariant-checking logic reverted in after having fixed
the issue with the root node, which may not be tracked if the sync
data was supplied by the USS migrator.

Bug: 915198
Change-Id: I2e3db80d14d8f4a07bc395e1fec46ff9af6a7b8c
Reviewed-by: Mikel Astiz <>
Commit-Queue: Mikel Astiz <>
Cr-Commit-Position: refs/heads/master@{#616994}
1 file changed