src/vs/editor/browser/widget/diffEditorWidget.ts/DiffEditorWidget/_createOverviewRulers
class DiffEditorWidget:	private _createOverviewRulers(): void {
		if (!this._options.renderOverviewRuler) {
			return;
		}

		assert.ok(!this._originalOverviewRuler && !this._modifiedOverviewRuler);

		if (this._originalEditor.hasModel()) {
			this._originalOverviewRuler = this._originalEditor.createOverviewRuler('original diffOverviewRuler')!;
			this._overviewDomElement.appendChild(this._originalOverviewRuler.getDomNode());
		}
		if (this._modifiedEditor.hasModel()) {
			this._modifiedOverviewRuler = this._modifiedEditor.createOverviewRuler('modified diffOverviewRuler')!;
			this._overviewDomElement.appendChild(this._modifiedOverviewRuler.getDomNode());
		}

		this._layoutOverviewRulers();
	}