Distinguish between SCT invalidity reasons in UMA

net/cert/ct_sct_to_string.cc

Index: net/cert/ct_sct_to_string.cc
diff --git a/net/cert/ct_sct_to_string.cc b/net/cert/ct_sct_to_string.cc
index f3912a828623240199ee30e628887d997a746aff..4d7449252b4a30ba273b23599114ef28027e35b5 100644
--- a/net/cert/ct_sct_to_string.cc
+++ b/net/cert/ct_sct_to_string.cc
@@ -62,14 +62,14 @@ const std::string StatusToString(SCTVerifyStatus status) {
   switch (status) {
     case SCT_STATUS_LOG_UNKNOWN:
       return "From unknown log";
-    case SCT_STATUS_INVALID:
-      return "Invalid";
+    case SCT_STATUS_INVALID_SIGNATURE:
+      return "Invalid signature";
     case SCT_STATUS_OK:
       return "Verified";
     case SCT_STATUS_NONE:
       return "None";
-    case SCT_STATUS_MAX:
-      NOTREACHED();
+    case SCT_STATUS_INVALID_TIMESTAMP:
+      return "Invalid timestamp";
   }
   return "Unknown";
 }