Make CPDF_Object::GetString() a virtual method.

fpdfsdk/src/fsdk_baseannot.cpp

Index: fpdfsdk/src/fsdk_baseannot.cpp
diff --git a/fpdfsdk/src/fsdk_baseannot.cpp b/fpdfsdk/src/fsdk_baseannot.cpp
index e35e537765986baa97325a0f679bf9fdbf8e68fc..78052d833bce6acf7db108bb7e5f179c43551800 100644
--- a/fpdfsdk/src/fsdk_baseannot.cpp
+++ b/fpdfsdk/src/fsdk_baseannot.cpp
@@ -685,7 +685,7 @@ void CPDFSDK_Annot::SetModifiedDate(const FX_SYSTEMTIME& st)
 FX_SYSTEMTIME CPDFSDK_Annot::GetModifiedDate() const
 {
 	FX_SYSTEMTIME systime;
-	CFX_ByteString str = m_pAnnot->GetAnnotDict()->GetString("M");
+	CFX_ByteString str = m_pAnnot->GetAnnotDict()->GetStringAt("M");
 
  	CPDFSDK_DateTime dt(str);
  	dt.ToSystemTime(systime);
@@ -713,7 +713,7 @@ void CPDFSDK_Annot::SetAppState(const CFX_ByteString& str)
 
 CFX_ByteString CPDFSDK_Annot::GetAppState() const
 {
-	return m_pAnnot->GetAnnotDict()->GetString("AS");
+	return m_pAnnot->GetAnnotDict()->GetStringAt("AS");
 }
 
 void CPDFSDK_Annot::SetStructParent(int key)
@@ -803,7 +803,7 @@ int	CPDFSDK_Annot::GetBorderStyle() const
 	CPDF_Dictionary* pBSDict = m_pAnnot->GetAnnotDict()->GetDict("BS");
 	if (pBSDict)
 	{
-		CFX_ByteString sBorderStyle = pBSDict->GetString("S", "S");
+		CFX_ByteString sBorderStyle = pBSDict->GetStringAt("S", "S");
 		if (sBorderStyle == "S") return BBS_SOLID;
 		if (sBorderStyle == "D") return BBS_DASH;
 		if (sBorderStyle == "B") return BBS_BEVELED;