Push up GetPrincipal to nsINode (as GetNodePrincipal). This way all nsINodes

(content, documents, attr nodes) can return their principal as needed.
Eliminate lazy allocation of principals in nsDocument.  Bug 324600, r=sicking, sr=jst

content/base/src/nsFrameLoader.cpp

@@ -162,7 +162,9 @@ nsFrameLoader::LoadURI(nsIURI* aURI)
     // to inherit an owner from the current document.
 
     loadInfo->SetInheritOwner(PR_TRUE);
-    principal = doc->GetPrincipal();
+    principal = mOwnerContent->GetNodePrincipal();
+    NS_ASSERTION(principal == doc->GetNodePrincipal(),
+                 "Principal mismatch.  Should not happen");
   }
 
   if (!principal) {