Anchor config broken in Firefox in ExtJS 6.5
The anchor config appears to have broken on Windows Firefox 50+ during ExtJS 6.5 - this works fine on Firefox versions less than 50, and also works fine on other browswers (IE11, Chrome 68); this also works fine using Firefox <50 and Ext <6.5 (e.g. Ext 6.0-Ext 6.2).
Using this trivial example you can reproduce the problem (although note, Fiddle doesn't actually work on Firefox 50+!?! could we please get the underlying Fiddle updated to Ext 6.5 so that it works on the most recent Firefox???).
When the screen is first displayed, the control is "invisible" - simply resizing the screen makes the control "visible" and everything afterwards seems to work fine.
Please also provide some kind of workaround until a fix is available because I need to provide a solution to our users now (and not have to wait for ExtJS 6.6.1 or whatever) - I tried adding code to force the viewport to "redraw" itself, but nothing that I tried worked: I tried adding a listener for boxready, render, and show events and then tried to updateLayout() and render() both the viewport itself and the underlying control, and none of those worked - and then just simply tried to do those same steps after the viewport was created, but that did not work either.
This is pretty critical and basically makes our software unusable on Firefox, please let me know if you need any additional information, thanks
