Use enum class for subtypes of CPDF_Annot.

fpdfsdk/cpdfsdk_widgethandler.cpp

Index: fpdfsdk/cpdfsdk_widgethandler.cpp
diff --git a/fpdfsdk/cpdfsdk_widgethandler.cpp b/fpdfsdk/cpdfsdk_widgethandler.cpp
index 0fb64dfaecd94d25ffa1034516369abf1de9728b..77e14f0404a9e36f68aa9b34eeda3c19911dfd63 100644
--- a/fpdfsdk/cpdfsdk_widgethandler.cpp
+++ b/fpdfsdk/cpdfsdk_widgethandler.cpp
@@ -27,12 +27,8 @@ CPDFSDK_WidgetHandler::CPDFSDK_WidgetHandler(CPDFDoc_Environment* pApp)
 
 CPDFSDK_WidgetHandler::~CPDFSDK_WidgetHandler() {}
 
-CFX_ByteString CPDFSDK_WidgetHandler::GetType() {
-  return CFX_ByteString("Widget");
-}
-
 FX_BOOL CPDFSDK_WidgetHandler::CanAnswer(CPDFSDK_Annot* pAnnot) {
-  ASSERT(pAnnot->GetAnnotSubtype() == "Widget");
+  ASSERT(pAnnot->GetAnnotSubtype() == CPDF_Annot::Subtype::WIDGET);
   if (pAnnot->IsSignatureWidget())
     return FALSE;