Problem/Motivation
In Settings Tray tests we have OutsideInJavascriptTestBase::waitForNoElement. This is used when an element will be removed from the page but we can't just check to see if it removed becase the Javascript to remove might take time and this could cause random failures.
Proposed resolution
Create \Drupal\FunctionalJavascriptTests\JSWebAssert::assertNoElementAfterWait()
This will be similar to \Drupal\FunctionalJavascriptTests\JSWebAssert::waitForElement but course there is no point in returning the element which should not be there.
Remaining tasks
Write patch
User interface changes
None
API changes
New test assert
Data model changes
None