src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts/OutputFocusTracker/_onBlur
class OutputFocusTracker:		private _onBlur() {
			if (this._hasFocus) {
				this._loosingFocus = true;
				window.setTimeout(() => {
					if (this._loosingFocus) {
						this._loosingFocus = false;
						this._hasFocus = false;
						postNotebookMessage<webviewMessages.IOutputBlurMessage>('outputBlur', {
							id: this._outputId,
						});
					}
				}, 0);
			}
		}