Update comments for net/data/verify_certificate_chain_unittest/

net/data/verify_certificate_chain_unittest/target-unknown-critical-extension/generate-chains.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. The target
-certificate has an unknown X.509v3 extension (OID=1.2.3.4) that is marked as
-critical. Verifying this certificate chain is expected to fail because there is
-an unrecognized critical extension."""
+"""Certificate chain where the target certificate contains an unknown X.509v3
+extension (OID=1.2.3.4) that is marked as critical."""
 
 import sys
 sys.path += ['..']
 
 import common
 
-# Self-signed root certificate (used as trust anchor).
+# Self-signed root certificate.
 root = common.create_self_signed_root_certificate('Root')
 
 # Intermediate certificate.
 intermediate = common.create_intermediate_certificate('Intermediate', root)
 
 # Target certificate (has unknown critical extension).
 target = common.create_end_entity_certificate('Target', intermediate)
 target.get_extensions().add_property('1.2.3.4',
                                      'critical,DER:01:02:03:04')
 
 chain = [target, intermediate, root]
 common.write_chain(__doc__, chain, 'chain.pem')