code: function(oldRange, newRange, oldText, newText)
      {
          if (!this._internalTextChangeMode)
              this._textModel.resetUndoStack();
          this._mainPanel.textChanged(oldRange, newRange);
          this._gutterPanel.textChanged(oldRange, newRange);
          this._updatePanelOffsets();
      }
docs: WebInspector.TextModel listener