function contentCallback(mimeType, content)
        {
            if (this._outlineWorker)
                this._outlineWorker.terminate();
            this._outlineWorker = new Worker("ScriptFormatterWorker.js");
            this._outlineWorker.onmessage = this._didBuildOutlineChunk.bind(this);
            const method = "outline";
            this._outlineWorker.postMessage({ method: method, params: { content: content, id: this.visibleView.uiSourceCode.id } });
        }
@param {WebInspector.UISourceCode} uiSourceCode
@return {WebInspector.SourceFrame}