Revert bug 410927 because it didn't really help perf and hurt codesize a little bit

xpcom/glue/nsID.h

@@ -81,7 +81,7 @@ struct nsID {
     // See bug http://bugzilla.mozilla.org/show_bug.cgi?id=164580 for
     // details.
 
-    return this == &other ||
+    return
       ((((PRUint32*) &m0)[0] == ((PRUint32*) &other.m0)[0]) &&
        (((PRUint32*) &m0)[1] == ((PRUint32*) &other.m0)[1]) &&
        (((PRUint32*) &m0)[2] == ((PRUint32*) &other.m0)[2]) &&