Add error information to VerifyCertificateChain().

net/data/verify_certificate_chain_unittest/generate-incorrect-trust-anchor.py

Index: net/data/verify_certificate_chain_unittest/generate-incorrect-trust-anchor.py
diff --git a/net/data/verify_certificate_chain_unittest/generate-unknown-root.py b/net/data/verify_certificate_chain_unittest/generate-incorrect-trust-anchor.py
similarity index 80%
rename from net/data/verify_certificate_chain_unittest/generate-unknown-root.py
rename to net/data/verify_certificate_chain_unittest/generate-incorrect-trust-anchor.py
index 7de9d67a72361101a0360f9335b9b8feabe5a908..92b4446d4b8b8dab33f3837085eab2bf11b7692c 100755
--- a/net/data/verify_certificate_chain_unittest/generate-unknown-root.py
+++ b/net/data/verify_certificate_chain_unittest/generate-incorrect-trust-anchor.py
@@ -3,9 +3,9 @@
 # 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, but the root is not in trust store.
-Verification is expected to fail because the final intermediate (Intermediate)
-does not chain to a known root."""
+"""Certificate chain with 1 intermediate, but the trust anchor used is
+incorrect (neither subject nor signature matches). Verification is expected to
+fail."""
 
 import common
 
@@ -26,5 +26,6 @@ chain = [target, intermediate]
 trusted = common.TrustAnchor(bogus_root, constrained=False)
 time = common.DEFAULT_TIME
 verify_result = False
+errors = ['Signature verification failed']
 
-common.write_test_file(__doc__, chain, trusted, time, verify_result)
+common.write_test_file(__doc__, chain, trusted, time, verify_result, errors)