Make CPDF_Object::GetString() a virtual method.

core/src/fpdfdoc/doc_viewerPreferences.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/fpdfdoc/fpdf_doc.h"
 CPDF_ViewerPreferences::CPDF_ViewerPreferences(CPDF_Document *pDoc): m_pDoc(pDoc)
 {
 }
 CPDF_ViewerPreferences::~CPDF_ViewerPreferences()
 {
 }
 FX_BOOL CPDF_ViewerPreferences::IsDirectionR2L() const
 {
     CPDF_Dictionary *pDict = m_pDoc->GetRoot();
     pDict = pDict->GetDict(FX_BSTRC("ViewerPreferences"));
-    if (!pDict) {
+    if (!pDict)
         return FALSE;
-    }
-    return FX_BSTRC("R2L") == pDict->GetString(FX_BSTRC("Direction"));
+    return pDict->GetStringAt("Direction") == "R2L";
 }
 FX_BOOL CPDF_ViewerPreferences::PrintScaling() const
 {
     CPDF_Dictionary *pDict = m_pDoc->GetRoot();
     pDict = pDict->GetDict(FX_BSTRC("ViewerPreferences"));
-    if (!pDict) {
+    if (!pDict)
         return TRUE;
-    }
-    return FX_BSTRC("None") != pDict->GetString(FX_BSTRC("PrintScaling"));
+    return pDict->GetStringAt("PrintScaling") != "None";
 }
 int32_t CPDF_ViewerPreferences::NumCopies() const
 {
     CPDF_Dictionary *pDict = m_pDoc->GetRoot();
     pDict = pDict->GetDict(FX_BSTRC("ViewerPreferences"));
     if (!pDict) {
         return 1;
     }
     return pDict->GetInteger(FX_BSTRC("NumCopies"));
 }
 CPDF_Array* CPDF_ViewerPreferences::PrintPageRange() const
 {
     CPDF_Dictionary *pDict = m_pDoc->GetRoot();
     CPDF_Array *pRange = NULL;
     pDict = pDict->GetDict(FX_BSTRC("ViewerPreferences"));
     if (!pDict) {
         return pRange;
     }
     pRange = pDict->GetArray(FX_BSTRC("PrintPageRange"));
     return pRange;
 }
 CFX_ByteString CPDF_ViewerPreferences::Duplex() const
 {
     CPDF_Dictionary *pDict = m_pDoc->GetRoot();
     pDict = pDict->GetDict(FX_BSTRC("ViewerPreferences"));
     if (!pDict) {
         return FX_BSTRC("None");
     }
-    return pDict->GetString(FX_BSTRC("Duplex"));
+    return pDict->GetStringAt("Duplex");
 }