Bug 433070 - Cannot import passwords from Seamonkey. r=gavin

browser/components/migration/src/nsSeamonkeyProfileMigrator.cpp

@@ -683,8 +683,9 @@ nsSeamonkeyProfileMigrator::CopyPasswords(PRBool aReplace)
     nsCOMPtr<nsILoginManagerStorage> importer(
         do_CreateInstance("@mozilla.org/login-manager/storage/legacy;1"));
 
-    nsCOMPtr<nsIFile> signonsFile(do_QueryInterface(mSourceProfile));
-    signonsFile->SetLeafName(fileName);
+    nsCOMPtr<nsIFile> signonsFile;
+    mSourceProfile->Clone(getter_AddRefs(signonsFile));
+    signonsFile->Append(fileName);
 
     importer->InitWithFile(signonsFile, nsnull);