Fix #22581 by introducing an artificial delay (#22601)

Introduce a delay into reports to allow visualizations time to appear in the DOM. This is intended as a temporary (and hacky) workaround until we come up with a more robust way to determine that all of the visualizations on the page are ready for capture.

x-pack/plugins/reporting/export_types/printable_pdf/server/lib/screenshots.js

@@ -133,7 +133,13 @@ export function screenshotsObservableFactory(server) {
  }
  }
 
- return Promise.all(renderedTasks);
+ // The renderComplete fires before the visualizations are in the DOM, so
+ // we wait for the event loop to flush before telling reporting to continue. This
+ // seems to correct a timing issue that was causing reporting to occasionally
+ // capture the first visualization before it was actually in the DOM.
+ const hackyWaitForVisualizations = () => new Promise(r => setTimeout(r, 100));
+
+ return Promise.all(renderedTasks).then(hackyWaitForVisualizations);
  },
  args: [layout.selectors.renderComplete, captureConfig.loadDelay],
  awaitPromise: true,