Support trust anchor constraints, by specifying them as a certificate.

net/data/verify_certificate_chain_unittest/generate-constrained-non-self-signed-root.py

 #!/usr/bin/python
 # Copyright (c) 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-"""Certificate chain with 1 intermediate and a trusted root. Verification is
-expected to succeed."""
+"""Certificate chain with 1 intermediate and a non-self-signed trust anchor.
+Verification should succeed, it doesn't matter that the root was not
+self-signed if it is designated as the trust anchor."""
 
 import common
 
-# Self-signed root certificate (used as trust anchor).
-root = common.create_self_signed_root_certificate('Root')
+uber_root = common.create_self_signed_root_certificate('UberRoot')
+
+# Non-self-signed root certificate (used as trust anchor)
+root = common.create_intermediate_certificate('Root', uber_root)
 
 # Intermediate certificate.
 intermediate = common.create_intermediate_certificate('Intermediate', root)
 
 # Target certificate.
 target = common.create_end_entity_certificate('Target', intermediate)
 
 chain = [target, intermediate]
-trusted = common.TrustAnchor(root, constrained=False)
+trusted = common.TrustAnchor(root, constrained=True)
 time = common.DEFAULT_TIME
 verify_result = True
 
 common.write_test_file(__doc__, chain, trusted, time, verify_result)
+