src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts/OutputFocusTracker/_onFocus
class OutputFocusTracker:		private _onFocus() {
			this._loosingFocus = false;
			if (!this._hasFocus) {
				this._hasFocus = true;
				postNotebookMessage<webviewMessages.IOutputFocusMessage>('outputFocus', {
					id: this._outputId,
				});
			}
		}