src/vs/workbench/browser/parts/titlebar/titlebarPart.ts/TitlebarPart/registerListeners
class TitlebarPart:	private registerListeners(): void {
		this._register(this.hostService.onDidChangeFocus(focused => focused ? this.onFocus() : this.onBlur()));
		this._register(this.configurationService.onDidChangeConfiguration(e => this.onConfigurationChanged(e)));
	}