bug 1181140 - Extract XRefBase base class
bug 1181140 - Extract XRefBase base class

mdn/browsercompat,mdn/browsercompat,jwhitlock/web-platform-compat,mdn/browsercompat,jwhitlock/web-platform-compat,renoirb/browsercompat,renoirb/browsercompat,renoirb/browsercompat,jwhitlock/web-platform-compat