Add error information to VerifyCertificateChain().

net/data/verify_certificate_chain_unittest/incorrect-trust-anchor.pem

Index: net/data/verify_certificate_chain_unittest/incorrect-trust-anchor.pem
diff --git a/net/data/verify_certificate_chain_unittest/unknown-root.pem b/net/data/verify_certificate_chain_unittest/incorrect-trust-anchor.pem
similarity index 97%
rename from net/data/verify_certificate_chain_unittest/unknown-root.pem
rename to net/data/verify_certificate_chain_unittest/incorrect-trust-anchor.pem
index 307abb7cd689e33f1952e968433bc70fc1799cb9..dad1d9ed2d29fa4c7d80e2771b8de3c5cc48c905 100644
--- a/net/data/verify_certificate_chain_unittest/unknown-root.pem
+++ b/net/data/verify_certificate_chain_unittest/incorrect-trust-anchor.pem
@@ -1,8 +1,8 @@
-[Created by: generate-unknown-root.py]
+[Created by: generate-incorrect-trust-anchor.py]
 
-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.
 
 Certificate:
     Data:
@@ -272,10 +272,17 @@ qXrrR8ubPuxCiS70KyA28fxw4juDCuA6BB6/U8u2yv4vJdXGqnE5qY4lSnW7Ffwp
 T7rWqQLHjdgGSKptCzS9Nhnqh6lQ5ajYMXOiMEQ=
 -----END TRUST_ANCHOR_UNCONSTRAINED-----
 
+150302120000Z
 -----BEGIN TIME-----
 MTUwMzAyMTIwMDAwWg==
 -----END TIME-----
 
+FAIL
 -----BEGIN VERIFY_RESULT-----
 RkFJTA==
 -----END VERIFY_RESULT-----
+
+Signature verification failed
+-----BEGIN ERRORS-----
+U2lnbmF0dXJlIHZlcmlmaWNhdGlvbiBmYWlsZWQ=
+-----END ERRORS-----