Fix classes that have too many virtuals for inline constructors.

net/quic/quic_connection.h

Index: net/quic/quic_connection.h
diff --git a/net/quic/quic_connection.h b/net/quic/quic_connection.h
index 971ec01bcf70736ac07a93ceca89fdb7d4726af7..f47baf0ae321f87d0b0f7d10636400609903656b 100644
--- a/net/quic/quic_connection.h
+++ b/net/quic/quic_connection.h
@@ -248,6 +248,9 @@ class NET_EXPORT_PRIVATE QuicConnectionDebugVisitor
   // Called when RTT may have changed, including when an RTT is read from
   // the config.
   virtual void OnRttChanged(QuicTime::Delta rtt) const {}
+
+ protected:
+  QuicConnectionDebugVisitor() = default;
 };
 
 class NET_EXPORT_PRIVATE QuicConnectionHelperInterface {