Leakless promise API

gistfile1.js

WebInspector.EventListener = function(thisObject, fireOnce)
{
    this._thisObject = thisObject;
    this._emitter = null;
    this._listener = null;
    this._fireOnce = fireOnce;
}

WebInspector.EventListener.prototype = {
    connect: function(emitter, type, listener, usesCapture)
    {
        console.assert(!this._emitter && !this._listener, "EventListener already bound.", this);
        console.assert(listener, "Missing listener for event: " + type);
        console.assert(emitter, "Missing event emitter for event: " + type);
        console.assert(emitter instanceof WebInspector.Object || emitter instanceof Node || (typeof emitter.addEventListener === "function"), "Event emitter", emitter, " (type:" + type + ") does not implement Node or WebInspector.Object!");

        this._emitter = emitter;
        this._type = type;
        this._usesCapture = usesCapture;

        if (emitter instanceof Node)
            listener = listener.bind(this._thisObject);

        if (this._fireOnce) {
            var receiver = this;
            this._listener = function() {
                receiver.disconnect();
                listener(...arguments);
            }
        } else
            this._listener = listener;

        if (this._emitter instanceof Node)
            this._emitter.addEventListener(this._type, this._listener, this._usesCapture);
        else
            this._emitter.addEventListener(this._type, this._listener, this._thisObject);
    },

    disconnect: function()
    {
        console.assert(this._emitter && this._listener, "EventListener is not bound.", this);

        if (this._emitter instanceof Node)
            this._emitter.removeEventListener(this._type, this._listener, this._usesCapture);
        else
            this._emitter.removeEventListener(this._type, this._listener, this._thisObject);

        this._thisObject = null;
        this._emitter = null;
        this._type = null;
        this._listener = null;
    }
};

DebuggerManager.prototype = {

//...

    pause: function()
    {
        if (this._paused)
            return Promise.resolve();

        listener = new WebInspector.EventListener(this, true);

        var managerResult = new Promise(function(resolve, reject) {
            listener.connect(WebInspector.debuggerManager, WebInspector.DebuggerManager.Event.Paused, resolve);
        });

        var protocolResult = DebuggerAgent.pause()
            .catch(function(error) {
                listener.disconnect();
                console.error("DebuggerManager.pause failed: ", error);
                throw error;
            });

        return new Promise.all([managerResult, protocolResult]);
    },
    
    // ...
    
}