Suspect that these additional regression test failures are also related to this, should be confirmed with the fix:

ICE-2367: Allow panelTabSet to change tabs without validation
ICE-1883: Partial submit disables previous validation messages

The old behaviour of this code was to restore the required attribute of the component during the post RenderResponse phase. This meant that if other components in the form have the partial submit flag set to true, the the "required" attribute setting of components may be artificially turned off during rendering. This attribute was being restored, but only after the post renderResponse phase listener.

This was a problem when state saving is turned on because state saving is capturing the state after rendering is done on the component, but before the end of the renderResponse phase. Due to the nature of our DOMResponseRenderer, it has to be done after rendering, but before the document is closed.

The solution is to restore the correct state of the attributes in the pre render response phase listener.

There could be some changes in behaviour in rendering but the underlying functionality of the 'required' attribute should not change.