Fix an out-of-boundary issue for wide string

core/include/fxcrt/fx_string.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 _FX_STRING_H_
 #define _FX_STRING_H_
 class CFX_ByteStringC;
 class CFX_ByteString;
@@ skipping 616 matching lines @@
     CFX_WideString(FX_WCHAR ch);
 
     CFX_WideString(const CFX_WideStringC& str);
 
     CFX_WideString(const CFX_WideStringC& str1, const CFX_WideStringC& str2);
 
     ~CFX_WideString();
 
     static CFX_WideString       FromLocal(const char* str, FX_STRSIZE len = -1);
 
-    static CFX_WideString       FromUTF8(const char* str, FX_STRSIZE len = -1);
+    static CFX_WideString       FromUTF8(const char* str, FX_STRSIZE len);
 
-    static CFX_WideString       FromUTF16LE(const unsigned short* str, FX_STRSIZE len = -1);
+    static CFX_WideString       FromUTF16LE(const unsigned short* str, FX_STRSIZE len);
 
     operator FX_LPCWSTR() const
     {
         return m_pData ? m_pData->m_String : (FX_WCHAR*)L"";
     }
 
     void                                        Empty();
 
 
     FX_BOOL                                     IsEmpty() const
@@ skipping 185 matching lines @@
 CFX_ByteString  FX_UTF8Encode(FX_LPCWSTR pwsStr, FX_STRSIZE len);
 inline CFX_ByteString   FX_UTF8Encode(FX_WSTR wsStr)
 {
     return FX_UTF8Encode(wsStr.GetPtr(), wsStr.GetLength());
 }
 inline CFX_ByteString   FX_UTF8Encode(const CFX_WideString &wsStr)
 {
     return FX_UTF8Encode((FX_LPCWSTR)wsStr, wsStr.GetLength());
 }
 #endif