Make CPDF_Object::GetString() a virtual method.

core/src/fpdfdoc/doc_formcontrol.cpp

Index: core/src/fpdfdoc/doc_formcontrol.cpp
diff --git a/core/src/fpdfdoc/doc_formcontrol.cpp b/core/src/fpdfdoc/doc_formcontrol.cpp
index 7fa17b8ffac011fa5179003da8580c69347f3ca6..f54a123a82e23b412d2edbf69549c05da8d664cd 100644
--- a/core/src/fpdfdoc/doc_formcontrol.cpp
+++ b/core/src/fpdfdoc/doc_formcontrol.cpp
@@ -46,7 +46,7 @@ void CPDF_FormControl::SetOnStateName(const CFX_ByteString& csOn)
     if (csValue == "Off") {
         csValue = "Yes";
     }
-    CFX_ByteString csAS = m_pWidgetDict->GetString("AS", "Off");
+    CFX_ByteString csAS = m_pWidgetDict->GetStringAt("AS", "Off");
     if (csAS != "Off") {
         m_pWidgetDict->SetAtName("AS", csValue);
     }
@@ -104,7 +104,7 @@ CFX_WideString CPDF_FormControl::GetExportValue()
         CPDF_Object* pOpt = FPDF_GetFieldAttr(m_pField->m_pDict, "Opt");
         if (pOpt != NULL && pOpt->GetType() == PDFOBJ_ARRAY) {
             int iIndex = m_pField->GetControlIndex(this);
-            csOn = ((CPDF_Array*)pOpt)->GetString(iIndex);
+            csOn = ((CPDF_Array*)pOpt)->GetStringAt(iIndex);
         }
     }
     if (csOn.IsEmpty()) {
@@ -117,7 +117,7 @@ FX_BOOL CPDF_FormControl::IsChecked()
 {
     ASSERT(GetType() == CPDF_FormField::CheckBox || GetType() == CPDF_FormField::RadioButton);
     CFX_ByteString csOn = GetOnStateName();
-    CFX_ByteString csAS = m_pWidgetDict->GetString("AS");
+    CFX_ByteString csAS = m_pWidgetDict->GetStringAt("AS");
     return csAS == csOn;
 }
 FX_BOOL CPDF_FormControl::IsDefaultChecked()
@@ -135,7 +135,7 @@ void CPDF_FormControl::CheckControl(FX_BOOL bChecked)
 {
     ASSERT(GetType() == CPDF_FormField::CheckBox || GetType() == CPDF_FormField::RadioButton);
     CFX_ByteString csOn = GetOnStateName();
-    CFX_ByteString csOldAS = m_pWidgetDict->GetString("AS", "Off");
+    CFX_ByteString csOldAS = m_pWidgetDict->GetStringAt("AS", "Off");
     CFX_ByteString csAS = "Off";
     if (bChecked) {
         csAS = csOn;
@@ -176,7 +176,7 @@ CPDF_FormControl::HighlightingMode CPDF_FormControl::GetHighlightingMode()
     if (m_pWidgetDict == NULL) {
         return Invert;
     }
-    CFX_ByteString csH = m_pWidgetDict->GetString("H", "I");
+    CFX_ByteString csH = m_pWidgetDict->GetStringAt("H", "I");
     int i = 0;
     while (g_sHighlightingMode[i][0] != '\0') {
         if (csH.Equal(g_sHighlightingMode[i])) {
@@ -277,7 +277,7 @@ CPDF_DefaultAppearance CPDF_FormControl::GetDefaultAppearance()
         return CFX_ByteString();
     }
     if (m_pWidgetDict->KeyExist("DA")) {
-        return m_pWidgetDict->GetString("DA");
+        return m_pWidgetDict->GetStringAt("DA");
     } else {
         CPDF_Object* pObj = FPDF_GetFieldAttr(m_pField->m_pDict, "DA");
         if (pObj == NULL) {