Add a histogram for session resumption version mismatches.

BUG=441456

Review URL: https://codereview.chromium.org/797693003

Cr-Commit-Position: refs/heads/master@{#308040}

net/socket/ssl_client_socket_openssl.cc

@@ -1131,9 +1131,18 @@ int SSLClientSocketOpenSSL::DoVerifyCertComplete(int result) {
     }
   }
 
-  if (result == OK)
+  if (result == OK) {
     RecordConnectionTypeMetrics(GetNetSSLVersion(ssl_));
 
+    if (SSL_session_reused(ssl_)) {
+      // Record whether or not the server tried to resume a session for a
+      // different version. See https://crbug.com/441456.
+      UMA_HISTOGRAM_BOOLEAN(
+          "Net.SSLSessionVersionMatch",
+          SSL_version(ssl_) == SSL_get_session(ssl_)->ssl_version);
+    }
+  }
+
   const CertStatus cert_status = server_cert_verify_result_.cert_status;
   if (transport_security_state_ &&
       (result == OK ||

tools/metrics/histograms/histograms.xml

@@ -19007,6 +19007,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.SSLSessionVersionMatch" enum="BooleanMatched">
+  <owner>davidben@chromium.org</owner>
+  <summary>
+    For each SSL connection that resumed a session, whether the session was
+    resumed at the same version it was established at. This is only recorded in
+    BoringSSL ports.
+  </summary>
+</histogram>
+
 <histogram name="Net.SSLv3FallbackToRenegoPatchedServer"
     enum="TLSRenegotiationPatched">
   <obsolete>