Fix an issue that no response from the call back function of FFI_GetLanguage()

fpdfsdk/src/javascript/app.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 "app.h"
 
 #include "Document.h"
 #include "JS_Context.h"
@@ skipping 210 matching lines @@
     vp << JS_STR_PLATFORM;
     return TRUE;
   }
 
   return FALSE;
 }
 
 FX_BOOL app::language(IJS_Context* cc,
                       CJS_PropValue& vp,
                       CFX_WideString& sError) {
-  if (vp.IsGetting()) {
+  if (!vp.IsGetting())
+    return FALSE;
+  CPDFDoc_Environment* pEnv =
+      static_cast<CJS_Context*>(cc)->GetJSRuntime()->GetReaderApp();
+  if (!pEnv)
+    return FALSE;
+  CFX_WideString language = pEnv->FFI_GetLanguage();
+  if (language.IsEmpty())
     vp << JS_STR_LANGUANGE;
-    return TRUE;
-  }
+  else
+    vp << language;
 
-  return FALSE;
+  return TRUE;
 }
 
 // creates a new fdf object that contains no data
 // comment: need reader support
 // note:
 // CFDF_Document * CPDFDoc_Environment::NewFDF();
 FX_BOOL app::newFDF(IJS_Context* cc,
                     const std::vector<CJS_Value>& params,
                     CJS_Value& vRet,
                     CFX_WideString& sError) {
@@ skipping 567 matching lines @@
 FX_BOOL app::media(IJS_Context* cc, CJS_PropValue& vp, CFX_WideString& sError) {
   return FALSE;
 }
 
 FX_BOOL app::execDialog(IJS_Context* cc,
                         const std::vector<CJS_Value>& params,
                         CJS_Value& vRet,
                         CFX_WideString& sError) {
   return TRUE;
 }