Return error information from pdfium to JS.

fpdfsdk/src/javascript/resource.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../include/javascript/resource.h"
 
 CFX_WideString JSGetStringFromID(CJS_Context* pContext, FX_UINT id)
 {
@@ skipping 21 matching lines @@
     case IDS_STRING_JSBUSY:
         return L"System is busy.";
     case IDS_STRING_JSEVENT:
         return L"Duplicate formfield event found.";
     case IDS_STRING_RUN:
         return L"Script ran successfully.";
     case IDS_STRING_JSPRINT1:
         return L"The second parameter can't be converted to a Date.";
     case IDS_STRING_JSPRINT2:
         return L"The second parameter is an invalid Date!";
-    case IDS_JSPARAM_INCORRECT:
+    case IDS_STRING_JSNOGLOBAL:
         return L"Global value not found.";
+    case IDS_STRING_JSREADONLY:
+        return L"Cannot assign to readonly property.";
     default:
         return L"";
     }
 }