Simplify UTF16LE_Encode and add unittest.

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 756 matching lines @@
     FX_STRSIZE                          Find(FX_LPCWSTR lpszSub, FX_STRSIZE start = 0) const;
 
     FX_STRSIZE                          Find(FX_WCHAR ch, FX_STRSIZE start = 0) const;
 
     FX_STRSIZE                          Replace(FX_LPCWSTR lpszOld, FX_LPCWSTR lpszNew);
 
     FX_STRSIZE                          Remove(FX_WCHAR ch);
 
     CFX_ByteString                      UTF8Encode() const;
 
-    CFX_ByteString                      UTF16LE_Encode(FX_BOOL bTerminate = TRUE) const;
+    CFX_ByteString                      UTF16LE_Encode() const;
 
     void                                        ConvertFrom(const CFX_ByteString& str, CFX_CharMap* pCharMap = NULL);
 protected:
     void                                        InitStr(FX_LPCWSTR ptr, int len);
 
     CFX_StringDataW*            m_pData;
     void                                        CopyBeforeWrite();
     void                                        AllocBeforeWrite(FX_STRSIZE nLen);
     void                                        ConcatInPlace(FX_STRSIZE nSrcLen, FX_LPCWSTR lpszSrcData);
     void                                        ConcatCopy(FX_STRSIZE nSrc1Len, FX_LPCWSTR lpszSrc1Data, FX_STRSIZE nSrc2Len, FX_LPCWSTR lpszSrc2Data);
@@ skipping 77 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(wsStr.c_str(), wsStr.GetLength());
 }
 #endif