Fix build failure.

test/core/channel/channel_stack_test.c

@@ -137,7 +137,8 @@ static void test_create_channel_stack(void) {
   call_stack = gpr_malloc(channel_stack->call_stack_size);
   grpc_error *error =
       grpc_call_stack_init(&exec_ctx, channel_stack, 1, free_call, call_stack,
-                           NULL, NULL, call_stack);
+                           NULL, NULL, gpr_inf_future(GPR_CLOCK_MONOTONIC),
+                           call_stack);
   GPR_ASSERT(error == GRPC_ERROR_NONE);
   GPR_ASSERT(call_stack->count == 1);
   call_elem = grpc_call_stack_element(call_stack, 0);