If you want to see what's in the Alfresco or Share WARs, just download them and expand them. Or look in the source which has always been and continues to be available at: https://svn.alfresco.com/repos/alfresco-open-mirror
If you've imported your Maven project into Eclipse, you'll see a list of Maven dependencies which includes Alfresco's JARs. If you click on any of those JARs, Eclipse will automatically find and download the corresponding source. Then you can set breakpoints and debug.
