Add parsing code for TBSCertificate's "validity" field.

net/data/parse_certificate_unittest/tbs_validity_both_generalized_time.pem

Index: net/data/parse_certificate_unittest/tbs_validity_both_generalized_time.pem
diff --git a/net/data/parse_certificate_unittest/tbs_v3_no_optionals.pem b/net/data/parse_certificate_unittest/tbs_validity_both_generalized_time.pem
similarity index 53%
copy from net/data/parse_certificate_unittest/tbs_v3_no_optionals.pem
copy to net/data/parse_certificate_unittest/tbs_validity_both_generalized_time.pem
index cc6fc04a4b3ef4fe0e8ebc8fdf1d8f01d612c06f..2b15076243acb6413c268de5ab77b8b2dd9bc28e 100644
--- a/net/data/parse_certificate_unittest/tbs_v3_no_optionals.pem
+++ b/net/data/parse_certificate_unittest/tbs_validity_both_generalized_time.pem
@@ -1,16 +1,16 @@
-This is a very basic TBSCertificate. It is valid from the perspective of
-ParseTbsCertificate(), however its sub-fields are mainly bogus. This
-TBSCertificate contains no optional fields (no issuerUniqueID, subjectUniqueID,
-extensions)
+SEQUENCE (2 elem)
+  GeneralizedTime  2014-01-31 00:00:00 UTC
+  GeneralizedTime  2016-02-29 00:00:00 UTC
 
 
 
 -----BEGIN TBS CERTIFICATE-----
-MCGgAwIBAgIBATADBAEBMAMEAQUwAwQBCDADBAEKMAMEAfM=
+MECgAwIBAgIBATADBAEBMAMEAQUwIhgPMjAxNDAxMzEwMDAwMDBaGA8yMDE2MDIyOTAwMDAwMFo
+wAwQBgzADBAHz
 -----END TBS CERTIFICATE-----
 
 $ openssl asn1parse -i < [TBS CERTIFICATE]
-    0:d=0  hl=2 l=  33 cons: SEQUENCE          
+    0:d=0  hl=2 l=  64 cons: SEQUENCE          
     2:d=1  hl=2 l=   3 cons:  cont [ 0 ]        
     4:d=2  hl=2 l=   1 prim:   INTEGER           :02
     7:d=1  hl=2 l=   1 prim:  INTEGER           :01
@@ -18,13 +18,13 @@ $ openssl asn1parse -i < [TBS CERTIFICATE]
    12:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:01
    15:d=1  hl=2 l=   3 cons:  SEQUENCE          
    17:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:05
-   20:d=1  hl=2 l=   3 cons:  SEQUENCE          
-   22:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:08
-   25:d=1  hl=2 l=   3 cons:  SEQUENCE          
-   27:d=2  hl=2 l=   1 prim:   OCTET STRING      :
-
-   30:d=1  hl=2 l=   3 cons:  SEQUENCE          
-   32:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:F3
+   20:d=1  hl=2 l=  34 cons:  SEQUENCE          
+   22:d=2  hl=2 l=  15 prim:   GENERALIZEDTIME   :20140131000000Z
+   39:d=2  hl=2 l=  15 prim:   GENERALIZEDTIME   :20160229000000Z
+   56:d=1  hl=2 l=   3 cons:  SEQUENCE          
+   58:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:83
+   61:d=1  hl=2 l=   3 cons:  SEQUENCE          
+   63:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:F3
 
 
 
@@ -54,23 +54,31 @@ $ openssl asn1parse -i < [ISSUER]
 
 
 
------BEGIN VALIDITY-----
-MAMEAQg=
------END VALIDITY-----
+-----BEGIN VALIDITY NOTBEFORE-----
+eWVhcj0yMDE0LCBtb250aD0xLCBkYXk9MzEsIGhvdXJzPTAsIG1pbnV0ZXM9MCwgc2Vjb25kcz0
+w
+-----END VALIDITY NOTBEFORE-----
 
-$ openssl asn1parse -i < [VALIDITY]
-    0:d=0  hl=2 l=   3 cons: SEQUENCE          
-    2:d=1  hl=2 l=   1 prim:  OCTET STRING      [HEX DUMP]:08
+VALIDITY NOTBEFORE: year=2014, month=1, day=31, hours=0, minutes=0, seconds=0
+
+
+
+-----BEGIN VALIDITY NOTAFTER-----
+eWVhcj0yMDE2LCBtb250aD0yLCBkYXk9MjksIGhvdXJzPTAsIG1pbnV0ZXM9MCwgc2Vjb25kcz0
+w
+-----END VALIDITY NOTAFTER-----
+
+VALIDITY NOTAFTER: year=2016, month=2, day=29, hours=0, minutes=0, seconds=0
 
 
 
 -----BEGIN SUBJECT-----
-MAMEAQo=
+MAMEAYM=
 -----END SUBJECT-----
 
 $ openssl asn1parse -i < [SUBJECT]
     0:d=0  hl=2 l=   3 cons: SEQUENCE          
-    2:d=1  hl=2 l=   1 prim:  OCTET STRING      :
+    2:d=1  hl=2 l=   1 prim:  OCTET STRING      [HEX DUMP]:83