Getting rid of more (FX_LPCWSTR) casts and fixing two bugs revealed by this.

core/src/fxcrt/fx_extension.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 "../../include/fxcrt/fx_ext.h"
 #include "extension.h"
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 #include <wincrypt.h>
@@ skipping 128 matching lines @@
 {
     return FXSYS_log(x) / FXSYS_log(b);
 }
 FX_FLOAT FXSYS_strtof(FX_LPCSTR pcsStr, FX_INT32 iLength, FX_INT32 *pUsedLen)
 {
     FXSYS_assert(pcsStr != NULL);
     if (iLength < 0) {
         iLength = (FX_INT32)FXSYS_strlen(pcsStr);
     }
     CFX_WideString ws = CFX_WideString::FromLocal(pcsStr, iLength);
-    return FXSYS_wcstof((FX_LPCWSTR)ws, iLength, pUsedLen);
+    return FXSYS_wcstof(ws.c_str(), iLength, pUsedLen);
 }
 FX_FLOAT FXSYS_wcstof(FX_LPCWSTR pwsStr, FX_INT32 iLength, FX_INT32 *pUsedLen)
 {
     FXSYS_assert(pwsStr != NULL);
     if (iLength < 0) {
         iLength = (FX_INT32)FXSYS_wcslen(pwsStr);
     }
     if (iLength == 0) {
         return 0.0f;
     }
@@ skipping 216 matching lines @@
 {
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
     FX_GenerateCryptoRandom(pBuffer, iCount);
 #else
     FX_Random_GenerateBase(pBuffer, iCount);
 #endif
 }
 #ifdef __cplusplus
 }
 #endif