function SignalBinding(fn, once, thisArg) {
        if (once === void 0) { once = false; }
        this._fn = fn;
        this._once = once;
        this._thisArg = thisArg;
        this._next = this._prev = this._owner = null;
    }
SignalBinding constructor.
@constructs SignalBinding
@param {Function} fn - Event handler to be called.
@param {boolean} [once=false] - Should this listener be removed after dispatch
@param {object} [thisArg] - The context of the callback function.
@api private