Convert FWL_ERR into an enum class.

xfa/fwl/lightwidget/cfwl_widgetdelegate.h

Index: xfa/fwl/lightwidget/cfwl_widgetdelegate.h
diff --git a/xfa/fwl/lightwidget/cfwl_widgetdelegate.h b/xfa/fwl/lightwidget/cfwl_widgetdelegate.h
index 42f6f9329f0ebcf7ce123fbeaed721c3c56af06b..f54399657b09e81c13b1de5fe16d176c52f4e4b2 100644
--- a/xfa/fwl/lightwidget/cfwl_widgetdelegate.h
+++ b/xfa/fwl/lightwidget/cfwl_widgetdelegate.h
@@ -7,6 +7,8 @@
 #ifndef XFA_FWL_LIGHTWIDGET_CFWL_WIDGETDELEGATE_H_
 #define XFA_FWL_LIGHTWIDGET_CFWL_WIDGETDELEGATE_H_
 
+#include <stdint.h>
+
 #include "xfa/fwl/core/fwl_error.h"
 #include "xfa/fwl/core/ifwl_widgetdelegate.h"
 
@@ -21,9 +23,9 @@ class CFWL_WidgetDelegate : public IFWL_WidgetDelegate {
   virtual ~CFWL_WidgetDelegate();
 
   int32_t OnProcessMessage(CFWL_Message* pMessage) override;
-  FWL_ERR OnProcessEvent(CFWL_Event* pEvent) override;
-  FWL_ERR OnDrawWidget(CFX_Graphics* pGraphics,
-                       const CFX_Matrix* pMatrix = nullptr) override;
+  FWL_Error OnProcessEvent(CFWL_Event* pEvent) override;
+  FWL_Error OnDrawWidget(CFX_Graphics* pGraphics,
+                         const CFX_Matrix* pMatrix = nullptr) override;
 };
 
 #endif  // XFA_FWL_LIGHTWIDGET_CFWL_WIDGETDELEGATE_H_