net: don't crash when failing dynamic pins.

ssl_client_socket_nss.cc calls ReportUMAOnPinFailure when pinning fails.
However, that function currently assumes that the pin failure came from a
built-in pin. When that's not the case, it hits a NULL pointer.

BUG=138521
TEST=none


Review URL: https://chromiumcodereview.appspot.com/10802067

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@147926 0039d316-1c4b-4281-b951-d872f2087c98

net/base/transport_security_state.cc

@@ -685,6 +685,11 @@ void TransportSecurityState::ReportUMAOnPinFailure(const std::string& host) {
                            kNumPreloadedSNISTS);
   }
 
+  if (!entry) {
+    // We don't care to report pin failures for dynamic pins.
+    return;
+  }
+
   DCHECK(entry);
   DCHECK(entry->pins.required_hashes);
   DCHECK(entry->second_level_domain_name != DOMAIN_NOT_PINNED);