Provides that, in any prosecution for a violation of RCW 9.35.010, 9.35.020, 9A.56.030, 9A.56.040, 9A.56.050, 9A.60.020, 9A.60.030, 9A.60.040, 9A.60.045, 9A.60.050, 9A.60.070, 18.27.020, or 21.20.400, if the victim of the offense was a vulnerable adult as defined in RCW 9A.44.010, the periods of limitation prescribed in RCW 9A.04.080 run from the date upon which the offense was discovered, or reasonably should have been discovered, whichever is earlier.