Scenario:

I've a custom store that is a content store, among other things.  Here is the
excerpt from Domain.xml:

<scope match="/files/Course Reports" store="xxxstore" />
<scope match="/" store="memory"/>

There is a link node /files/root/resources/Course Reports/ that points to
/files/Course Reports/root.

Now, when I call content.retrieve() to retrieve /files/Course
Reports/root/someFile.txt, I would expect that the xxxstore's
retrieveRevisionDescriptors() is executed.  As it turns out, it is calling
memory's retrieveRevisionDescriptors().