libsnapshot: RemoveUpdateState on rollback. am: ae2558d9

    // If all snapshots were reflashed, then cancel the entire update.

    if (AreAllSnapshotsCancelled(lock)) {

        LOG(WARNING) << "Detected re-flashing, cancelling unverified update.";

        RemoveAllUpdateState(lock, before_cancel);

        return true;

    }

    // This unverified update might be rolled back, or it might not (b/147347110

    // comment #77). Take no action, as update_engine is responsible for deciding

    // whether to cancel.

    LOG(ERROR) << "Update state is being processed before reboot, taking no action.";

    // If update has been rolled back, then cancel the entire update.

    // Client (update_engine) is responsible for doing additional cleanup work on its own states

    // when ProcessUpdateState() returns UpdateState::Cancelled.

    auto current_slot = GetCurrentSlot();

    if (current_slot != Slot::Source) {

        LOG(INFO) << "Update state is being processed while booting at " << current_slot

                  << " slot, taking no action.";

        return false;

    }

    // current_slot == Source. Attempt to detect rollbacks.

    if (access(GetRollbackIndicatorPath().c_str(), F_OK) != 0) {

        // This unverified update is not attempted. Take no action.

        PLOG(INFO) << "Rollback indicator not detected. "

                   << "Update state is being processed before reboot, taking no action.";

        return false;

    }

    LOG(WARNING) << "Detected rollback, cancelling unverified update.";

    RemoveAllUpdateState(lock, before_cancel);

    return true;

}

std::unique_ptr<LpMetadata> SnapshotManager::ReadCurrentMetadata() {

    const auto& opener = device_->GetPartitionOpener();

    uint32_t slot = SlotNumberForSlotSuffix(device_->GetSlotSuffix());