Remove CLASSHASH defines in favour of an enum class.

xfa/fwl/theme/cfwl_scrollbartp.h

Index: xfa/fwl/theme/cfwl_scrollbartp.h
diff --git a/xfa/fwl/theme/cfwl_scrollbartp.h b/xfa/fwl/theme/cfwl_scrollbartp.h
index b102ee45251b0287c8f0be7c344d05f8da47f6e3..84e18193db721d261cbcd5383f9ac3490df8f364 100644
--- a/xfa/fwl/theme/cfwl_scrollbartp.h
+++ b/xfa/fwl/theme/cfwl_scrollbartp.h
@@ -12,14 +12,16 @@
 class CFWL_ScrollBarTP : public CFWL_WidgetTP {
  public:
   CFWL_ScrollBarTP();
-  virtual ~CFWL_ScrollBarTP();
-  virtual FX_BOOL IsValidWidget(IFWL_Widget* pWidget);
-  virtual uint32_t SetThemeID(IFWL_Widget* pWidget,
-                              uint32_t dwThemeID,
-                              FX_BOOL bChildren = TRUE);
-  virtual FX_BOOL DrawBackground(CFWL_ThemeBackground* pParams);
-  virtual void* GetCapacity(CFWL_ThemePart* pThemePart,
-                            CFWL_WidgetCapacity dwCapacity);
+  ~CFWL_ScrollBarTP() override;
+
+  // CFWL_WidgetTP
+  bool IsValidWidget(IFWL_Widget* pWidget) override;
+  uint32_t SetThemeID(IFWL_Widget* pWidget,
+                      uint32_t dwThemeID,
+                      FX_BOOL bChildren = TRUE) override;
+  FX_BOOL DrawBackground(CFWL_ThemeBackground* pParams) override;
+  void* GetCapacity(CFWL_ThemePart* pThemePart,
+                    CFWL_WidgetCapacity dwCapacity) override;
 
  protected:
   struct SBThemeData {