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

net/data/verify_certificate_chain_unittest/generate-constrained-root-lacks-basic-constraints.py

Index: net/data/verify_certificate_chain_unittest/generate-constrained-root-lacks-basic-constraints.py
diff --git a/net/data/verify_certificate_chain_unittest/generate-target-and-intermediate.py b/net/data/verify_certificate_chain_unittest/generate-constrained-root-lacks-basic-constraints.py
similarity index 65%
copy from net/data/verify_certificate_chain_unittest/generate-target-and-intermediate.py
copy to net/data/verify_certificate_chain_unittest/generate-constrained-root-lacks-basic-constraints.py
index c426854857967b58f5cfbe8f72e53dbe214d9775..e9015f16fcbaf184446bfcf2067ce85dd3fa5289 100755
--- a/net/data/verify_certificate_chain_unittest/generate-target-and-intermediate.py
+++ b/net/data/verify_certificate_chain_unittest/generate-constrained-root-lacks-basic-constraints.py
@@ -3,22 +3,24 @@
 # 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 trust anchor. The trust anchor
+lacks the basic constraints extension, and is loaded with anchor constraints.
+This is not a problem and verification should succeed."""
 
 import common
 
 # Self-signed root certificate (used as trust anchor).
 root = common.create_self_signed_root_certificate('Root')
+root.get_extensions().remove_property('basicConstraints')
 
-# Intermediate certificate.
+# Intermediate.
 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