Added test for util.printx() and make it match spec.

fpdfsdk/javascript/util.h

 // 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
 
 #ifndef FPDFSDK_JAVASCRIPT_UTIL_H_
 #define FPDFSDK_JAVASCRIPT_UTIL_H_
 
 #include <string>
@@ skipping 20 matching lines @@
                  CFX_WideString& sError);
   FX_BOOL scand(IJS_Context* cc,
                 const std::vector<CJS_Value>& params,
                 CJS_Value& vRet,
                 CFX_WideString& sError);
   FX_BOOL byteToChar(IJS_Context* cc,
                      const std::vector<CJS_Value>& params,
                      CJS_Value& vRet,
                      CFX_WideString& sError);
 
-  static void printx(const std::string& cFormat,
-                     const std::string& cSource,
-                     std::string& cPurpose);
+  static CFX_WideString printx(const CFX_WideString& cFormat,
+                               const CFX_WideString& cSource);
 };
 
 class CJS_Util : public CJS_Object {
  public:
   CJS_Util(v8::Local<v8::Object> pObject) : CJS_Object(pObject) {}
   ~CJS_Util() override {}
 
   DECLARE_JS_CLASS();
 
   JS_STATIC_METHOD(printd, util);
   JS_STATIC_METHOD(printf, util);
   JS_STATIC_METHOD(printx, util);
   JS_STATIC_METHOD(scand, util);
   JS_STATIC_METHOD(byteToChar, util);
 };
 
 #endif  // FPDFSDK_JAVASCRIPT_UTIL_H_