After hunting down numerous flexbox pages to test each feature it has become clear that we really need a page that can be used to switch all properties of a flexbox. This test file should: - Allow the switching of all flexbox properties as well as those related to RTL and writing mode. - Allow us to bookmark the URL in order to preserve all settings. - Have a very simple HTML structure. This will speed up development greatly and help discover / minimize bugs.

Created a decent test file at: https://mikeratcliffe.github.io/BrowserTestFiles/flexbox.html In addition to the above it preserves each change in history and is the most complete example I can find anywhere. The code and theme could be tidier but this is just a test file after all.

I don't think this was supposed to be a [dt-q] bug, so I'm removing the whiteboard flag now.