fixing code that relied on implicit string construction. r=scc

xpinstall/src/nsRegisterItem.cpp

@@ -97,9 +97,9 @@ hack_nsIFile2URL(nsIFile* file, char * *aURL)
     SwapSlashColon(ePath);
 #endif
     // Escape the path with the directory mask
-    nsCAutoString tmp = ePath;
+    nsCAutoString tmp(ePath);
     tmp.ReplaceChar(":", '|');
-    nsCAutoString escPath = "file://";
+    nsCAutoString escPath("file://");
 	escPath += tmp;
 //    rv = nsURLEscape(ePath,nsIIOService::url_Directory + nsIIOService::url_Forced, escPath);
 //    if (NS_SUCCEEDED(rv)) {