Merge "Add a checker for signature boundary in verifier am: 54ea136fde am: 0a34b17c8b am: fb80b4f72d am: d3d5e54a45 am: 6ea9888d51 am: a055eb93c3 am: 15ca2a4763 am: ca50d7b66a am: 64f0de7a13 am: e4ec60e045 am: e0d3b0ceab am: f127896675" into nyc-mr2-dev-plus-aosp