Make JSGenerateToJSObject the default behavior and always generate the toJS() function, even if the interface has a parent. I verified locally that it doesn't increase the size of the WebCore binary. Missing JSGenerateToJSObject the IDL can lead to hard to diagnose crashes / bugs when implementing new Web APIs. Having a toJS() for the subclass is also better for performance than relying on the toJS() from a base class which has to do type checking.