Browser versions and OS (and desktop environment, if applicable)
Firefox/Chrome/IE9 Windows 7
Creating a Popup with setShadow(true) does not produce a shadow on the popup when shown.
Dev mode and production
Steps to reproduce the problem
Create a Popup instance
Call setShadow(true) on the Popup
Add content to the popup
Show the popup on the screen, there's no shadow
The shadow would have appeared
There was no shadow
Screenshot or video
Debugging already done
Looked at the source to figure out how Component subclasses normally get their shadow in the onAfterFirstAttach method, then saw how the Popup class overrides the onFirstAttach method without calling to the superclass. I created my own Popup subclass, overrode the 'onAfterFirstAttach' to create a new layer, enable shadow on the layer, and set the shadow position; my override caused the shadow to show correctly.
Call super.onAfterFirstAttach from the Popup class' override, or add in code to create and attach a shadow layer for Popup instances.