Only render notebook container if visible (#188226)

Co-authored-by: Peng Lyu 

Author: christian-bromann

src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts

@@ -1826,7 +1826,9 @@ export class NotebookEditorWidget extends Disposable implements INotebookEditorD
 		this._overlayContainer.style.position = 'absolute';
 		this._overlayContainer.style.overflow = 'hidden';
 
-		this.layoutContainerOverShadowElement(dimension, position);
+		if (this._isVisible) {
+			this.layoutContainerOverShadowElement(dimension, position);
+		}
 
 		if (this._webviewTransparentCover) {
 			this._webviewTransparentCover.style.height = `${dimension.height}px`;