private void index(Set<TrustAnchor> anchors) {
        for (TrustAnchor anchor : anchors) {
            index(anchor);
        }
    }
Indexes {@code TrustAnchor} instances so they can be found in O(1)
time instead of O(N).
common/src/main/java/org/conscrypt/TrustedCertificateIndex.java