Assert that CFX_ strings are pointer-size.

core/fxcrt/fx_basic_wstring.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 <stddef.h>
 
 #include <algorithm>
 #include <cctype>
@@ skipping 41 matching lines @@
         return haystack;
       }
     }
     haystack++;
   }
   return nullptr;
 }
 
 }  // namespace
 
+static_assert(sizeof(CFX_WideString) <= sizeof(FX_WCHAR*),
+              "Strings must not require more space than pointers");
+
 CFX_WideString::CFX_WideString(const FX_WCHAR* pStr, FX_STRSIZE nLen) {
   if (nLen < 0)
     nLen = pStr ? FXSYS_wcslen(pStr) : 0;
 
   if (nLen)
     m_pData.Reset(StringData::Create(pStr, nLen));
 }
 
 CFX_WideString::CFX_WideString(FX_WCHAR ch) {
   m_pData.Reset(StringData::Create(1));
@@ skipping 911 matching lines @@
       FXSYS_MultiByteToWideChar(codepage, 0, bstr.c_str(), src_len, nullptr, 0);
   CFX_WideString wstr;
   if (dest_len) {
     FX_WCHAR* dest_buf = wstr.GetBuffer(dest_len);
     FXSYS_MultiByteToWideChar(codepage, 0, bstr.c_str(), src_len, dest_buf,
                               dest_len);
     wstr.ReleaseBuffer(dest_len);
   }
   return wstr;
 }