add missing virtual dtor
diff --git a/src/core/ext/filters/client_channel/resolving_lb_policy.h b/src/core/ext/filters/client_channel/resolving_lb_policy.h
index 98ea37f..b44dc1a 100644
--- a/src/core/ext/filters/client_channel/resolving_lb_policy.h
+++ b/src/core/ext/filters/client_channel/resolving_lb_policy.h
@@ -68,6 +68,8 @@
       RefCountedPtr<LoadBalancingPolicy::Config> lb_policy_config;
     };
 
+    virtual ~ChannelConfigHelper() = default;
+
     // Applies the service config to the channel.
     virtual ApplyServiceConfigResult ApplyServiceConfig(
         const Resolver::Result& result) = 0;