Use std::unordered_map for CFDE_CSSStyleSheet::m_StringCache

xfa/fde/css/fde_cssstylesheet.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 XFA_FDE_CSS_FDE_CSSSTYLESHEET_H_
 #define XFA_FDE_CSS_FDE_CSSSTYLESHEET_H_
 
+#include <unordered_map>
+
 #include "core/fxcrt/include/fx_ext.h"
 #include "xfa/fde/css/fde_cssdeclaration.h"
 
 class CFDE_CSSSyntaxParser;
 
 class CFDE_CSSSelector : public CFX_Target {
  public:
   CFDE_CSSSelector(FDE_CSSSELECTORTYPE eType,
                    const FX_WCHAR* psz,
                    int32_t iLen,
@@ skipping 107 matching lines @@
   FDE_CSSSYNTAXSTATUS LoadFontFaceRule(CFDE_CSSSyntaxParser* pSyntax,
                                        CFDE_CSSRuleArray& ruleArray);
   FDE_CSSSYNTAXSTATUS SkipRuleSet(CFDE_CSSSyntaxParser* pSyntax);
   uint16_t m_wCodePage;
   uint16_t m_wRefCount;
   uint32_t m_dwMediaList;
   IFX_MemoryAllocator* m_pAllocator;
   CFDE_CSSRuleArray m_RuleArray;
   CFX_WideString m_szUrl;
   CFDE_CSSSelectorArray m_Selectors;
-  CFX_MapPtrToPtr m_StringCache;
+  std::unordered_map<uint32_t, FX_WCHAR*> m_StringCache;
 };
 
 #endif  // XFA_FDE_CSS_FDE_CSSSTYLESHEET_H_