Re-land patch for bug 83536, merging principal objects.

Also includes fixes from bug 216041.
r=bzbarsky
sr=jst


git-svn-id: svn://10.0.0.236/trunk@148229 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/xpinstall/src/nsSoftwareUpdateRun.cpp

@@ -55,7 +55,6 @@
 
 #include "nsIJAR.h"
 #include "nsIPrincipal.h"
-#include "nsICertificatePrincipal.h"
 
 static NS_DEFINE_CID(kSoftwareUpdateCID,  NS_SoftwareUpdate_CID);
 static NS_DEFINE_CID(kEventQueueServiceCID, NS_EVENTQUEUESERVICE_CID);
@@ -82,8 +81,9 @@ nsresult VerifySigning(nsIZipReader* hZip, nsIPrincipal* aPrincipal)
     if (!aPrincipal) 
         return NS_OK; // not signed, but not an error
 
-    nsCOMPtr<nsICertificatePrincipal> cp(do_QueryInterface(aPrincipal));
-    if (!cp) 
+    PRBool hasCert;
+    aPrincipal->GetHasCertificate(&hasCert);
+    if (!hasCert)
         return NS_ERROR_FAILURE;
 
     nsCOMPtr<nsIJAR> jar(do_QueryInterface(hZip));