src/vs/editor/browser/widget/diffEditorWidget.ts/DiffEditorWidget/_disposeOverviewRulers
class DiffEditorWidget:	private _disposeOverviewRulers(): void {
		if (this._originalOverviewRuler) {
			this._overviewDomElement.removeChild(this._originalOverviewRuler.getDomNode());
			this._originalOverviewRuler.dispose();
			this._originalOverviewRuler = null;
		}
		if (this._modifiedOverviewRuler) {
			this._overviewDomElement.removeChild(this._modifiedOverviewRuler.getDomNode());
			this._modifiedOverviewRuler.dispose();
			this._modifiedOverviewRuler = null;
		}
	}