Don't pass null isolates to FXJS_ when we have a real isolate.

fpdfsdk/src/javascript/JS_Runtime.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/JavaScript.h"
 #include "../../include/javascript/IJavaScript.h"
 #include "../../include/javascript/JS_EventHandler.h"
 #include "../../include/javascript/JS_Runtime.h"
@@ skipping 166 matching lines @@
         v8::Local<v8::Context>::New(m_isolate, m_context);
     v8::Context::Scope context_scope(context);
 
     m_pDocument = pReaderDoc;
     if (pReaderDoc) {
       v8::Local<v8::Object> pThis = FXJS_GetThisObj(GetIsolate());
       if (!pThis.IsEmpty()) {
         if (FXJS_GetObjDefnID(pThis) ==
             FXJS_GetObjDefnID(GetIsolate(), L"Document")) {
           if (CJS_Document* pJSDocument =
-                  (CJS_Document*)FXJS_GetPrivate(pThis)) {
+                  (CJS_Document*)FXJS_GetPrivate(GetIsolate(), pThis)) {
             if (Document* pDocument = (Document*)pJSDocument->GetEmbedObject())
               pDocument->AttachDoc(pReaderDoc);
           }
         }
       }
     }
   }
 }
 
 FX_BOOL CJS_Runtime::AddEventToLoop(const CFX_WideString& sTargetName,
@@ skipping 69 matching lines @@
 
 v8::Local<v8::Context> CJS_Runtime::NewJSContext() {
   return v8::Local<v8::Context>::New(m_isolate, m_context);
 }
 
 CFX_WideString ChangeObjName(const CFX_WideString& str) {
   CFX_WideString sRet = str;
   sRet.Replace(L"_", L".");
   return sRet;
 }