Avoid dubious use of comma operator in fde_csssyntax.h

xfa/fde/css/fde_csssyntax.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_CSSSYNTAX_H_
 #define XFA_FDE_CSS_FDE_CSSSYNTAX_H_
 
 #include "xfa/fde/css/fde_css.h"
 #include "xfa/fgas/crt/fgas_memory.h"
 #include "xfa/fgas/crt/fgas_stream.h"
 
 class CFDE_CSSTextBuf : public CFX_Target {
  public:
   CFDE_CSSTextBuf();
   ~CFDE_CSSTextBuf() override;
 
   FX_BOOL AttachBuffer(const FX_WCHAR* pBuffer, int32_t iBufLen);
   FX_BOOL EstimateSize(int32_t iAllocSize);
   int32_t LoadFromStream(IFX_Stream* pTxtStream,
                          int32_t iStreamOffset,
                          int32_t iMaxChars,
                          FX_BOOL& bEOS);
-  FX_BOOL AppendChar(FX_WCHAR wch) {
-    if (m_iDatLen >= m_iBufLen && !ExpandBuf(m_iBufLen * 2)) {
-      return FALSE;
-    }
-    return (m_pBuffer[m_iDatLen++] = wch), TRUE;
+  bool AppendChar(FX_WCHAR wch) {
+    if (m_iDatLen >= m_iBufLen && !ExpandBuf(m_iBufLen * 2))
+      return false;
+    m_pBuffer[m_iDatLen++] = wch;
+    return true;
   }
   void Clear() { m_iDatPos = m_iDatLen = 0; }
   void Reset();
   int32_t TrimEnd() {
     while (m_iDatLen > 0 && m_pBuffer[m_iDatLen - 1] <= ' ') {
       --m_iDatLen;
     }
     AppendChar(0);
     return --m_iDatLen;
   }
@@ skipping 72 matching lines @@
   CFDE_CSSTextBuf m_TextData;
   CFDE_CSSTextBuf m_TextPlane;
   int32_t m_iTextDatLen;
   uint32_t m_dwCheck;
   FDE_CSSSYNTAXMODE m_eMode;
   FDE_CSSSYNTAXSTATUS m_eStatus;
   CFX_StackTemplate<FDE_CSSSYNTAXMODE> m_ModeStack;
 };
 
 #endif  // XFA_FDE_CSS_FDE_CSSSYNTAX_H_