src/vs/workbench/contrib/preferences/browser/settingsTree.ts/AbstractSettingRenderer/addSettingElementFocusHandler
class AbstractSettingRenderer:	protected addSettingElementFocusHandler(template: ISettingItemTemplate): void {
		const focusTracker = DOM.trackFocus(template.containerElement);
		template.toDispose.add(focusTracker);
		focusTracker.onDidBlur(() => {
			if (template.containerElement.classList.contains('focused')) {
				template.containerElement.classList.remove('focused');
			}
		});

		focusTracker.onDidFocus(() => {
			template.containerElement.classList.add('focused');

			if (template.context) {
				this._onDidFocusSetting.fire(template.context);
			}
		});
	}