Issue reporter data overlay doesn't include screenshot

Steps to reproduce

1. Report an issue for a page and follow process
2. Click on "Click this link to review the report data before sending" to open data overlay
3. Open DevTools window and switch to network tab
4. Close data overlay and click on "Send report" (ideally, without a network connection to avoid creating bogus reports on server)

Observed behavior

For (2): Data overlay doesn't include <screenshot> element. For (4): DevTools show that <screenshot> element is included in sent report.

Expected behavior

For (2): Data overlay includes <screenshot> element. For (4): DevTools show that <screenshot> element is included in sent report.