ScreenshotBocDateTimeValuePickerExtensions.WaitUntilVisible does not always wait long enough

BocDateTimeValueControlObjectTest.ScreenshotTest_DatePicker failes sometimes with the following message:

When hosting the test site for the first time with IISExpress, opening the DatePicker loads the iframe immediately, but the content rendering is delayed. This does not happen when executing the test a second time without rebuilding the test site and could be related to the delayed generation of the datepickerform.aspx.XXXXXXXX.compiled file.

Reproducible with Chrome v77:

1. Delete temp ASP.NET files (Remove-Item -Recurse "$env:temp\Temporary ASP.NET Files\root")

2. Execute BocDateTimeValueControlObjectTest.ScreenshotTest_DatePicker()