Fix some issues with CXFA_FMParse/CXFA_FMLexer infinite looping.

xfa/src/fxfa/src/fm2js/xfa_lexer.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_FM_LEXER_H
 #define _XFA_FM_LEXER_H
+
+#include <memory>
+
 enum XFA_FM_TOKEN {
   TOKand,
   TOKlparen,
   TOKrparen,
   TOKmul,
   TOKplus,
   TOKcomma,
   TOKminus,
   TOKdot,
   TOKdiv,
@@ skipping 50 matching lines @@
   TOKstar,
   TOKidentifier,
   TOKunderscore,
   TOKdollar,
   TOKexclamation,
   TOKcall,
   TOKstring,
   TOKnumber,
   TOKreserver
 };
+
 struct XFA_FMKeyword {
   XFA_FM_TOKEN m_type;
   uint32_t m_uHash;
   const FX_WCHAR* m_keword;
 };
+
 const FX_WCHAR* XFA_FM_KeywordToString(XFA_FM_TOKEN op);
+
 class CXFA_FMToken {
  public:
   CXFA_FMToken();
-  CXFA_FMToken(FX_DWORD uLineNum);
-  ~CXFA_FMToken();
+  explicit CXFA_FMToken(FX_DWORD uLineNum);
+
   CFX_WideStringC m_wstring;
   XFA_FM_TOKEN m_type;
   FX_DWORD m_uLinenum;
-  CXFA_FMToken* m_pNext;
 };
+
 class CXFA_FMLexer {
  public:
   CXFA_FMLexer(const CFX_WideStringC& wsFormcalc, CXFA_FMErrorInfo* pErrorInfo);
-  ~CXFA_FMLexer();
   CXFA_FMToken* NextToken();
   FX_DWORD Number(CXFA_FMToken* t, const FX_WCHAR* p, const FX_WCHAR*& pEnd);
   FX_DWORD String(CXFA_FMToken* t, const FX_WCHAR* p, const FX_WCHAR*& pEnd);
   FX_DWORD Identifiers(CXFA_FMToken* t,
                        const FX_WCHAR* p,
                        const FX_WCHAR*& pEnd);
   void Comment(const FX_WCHAR* p, const FX_WCHAR*& pEnd);
   XFA_FM_TOKEN IsKeyword(const CFX_WideStringC& p);
   void SetCurrentLine(FX_DWORD line) { m_uCurrentLine = line; }
   void SetToken(CXFA_FMToken* pToken) {
-    if (m_pToken) {
-      delete m_pToken;
-    }
-    m_pToken = pToken;
+    if (m_pToken.get() != pToken)
+      m_pToken.reset(pToken);
   }
   const FX_WCHAR* SavePos() { return m_ptr; }
   void RestorePos(const FX_WCHAR* pPos) { m_ptr = pPos; }
   void Error(XFA_FM_ERRMSG msg, ...);
   FX_BOOL HasError() const;
 
  protected:
   CXFA_FMToken* Scan();
-  const FX_WCHAR* m_pScript;
+
   const FX_WCHAR* m_ptr;
-  FX_STRSIZE m_uLength;
   FX_DWORD m_uCurrentLine;
-  CXFA_FMToken* m_pToken;
+  std::unique_ptr<CXFA_FMToken> m_pToken;
   CXFA_FMErrorInfo* m_pErrorInfo;
 };
+
 #endif