src/vs/editor/contrib/gotoSymbol/peek/referencesController.ts/ReferencesController/changeFocusBetweenPreviewAndReferences
class ReferencesController:	changeFocusBetweenPreviewAndReferences() {
		if (!this._widget) {
			// can be called while still resolving...
			return;
		}
		if (this._widget.isPreviewEditorFocused()) {
			this._widget.focusOnReferenceTree();
		} else {
			this._widget.focusOnPreviewEditor();
		}
	}