Add POC example of inheritance for testing

src/core/ext/transport/chttp2/transport/chttp2_transport.cc

@@ -274,6 +274,9 @@ static void init_transport(grpc_exec_ctx* exec_ctx, grpc_chttp2_transport* t,
   GPR_ASSERT(strlen(GRPC_CHTTP2_CLIENT_CONNECT_STRING) ==
              GRPC_CHTTP2_CLIENT_CONNECT_STRLEN);
 
+  t->abstract = new D1;
+  t->abstract->foo();
+
   t->base.vtable = get_vtable();
   t->ep = ep;
   /* one ref is for destroy */

src/core/ext/transport/chttp2/transport/internal.h

@@ -237,12 +237,26 @@ typedef enum {
   GRPC_CHTTP2_KEEPALIVE_STATE_DISABLED,
 } grpc_chttp2_keepalive_state;
 
+class AbstractBase {
+ public:
+  AbstractBase() {}
+  virtual void foo() { gpr_log(GPR_ERROR, "base"); }
+};
+
+class D1 : public AbstractBase {
+ public:
+  D1() {}
+  void foo() override { gpr_log(GPR_ERROR, "derived"); }
+};
+
 struct grpc_chttp2_transport {
   grpc_transport base; /* must be first */
   gpr_refcount refs;
   grpc_endpoint* ep;
   char* peer_string;
 
+  AbstractBase* abstract;
+
   grpc_combiner* combiner;
 
   /** write execution state of the transport */