Change IFWL_Widget to store a single delegate.

xfa/fwl/core/ifwl_widget.h

Index: xfa/fwl/core/ifwl_widget.h
diff --git a/xfa/fwl/core/ifwl_widget.h b/xfa/fwl/core/ifwl_widget.h
index 264ff67513396f4474c17609028a0ed2c2e80e05..e00998c39e8540fc0094457ae5bcb9c4246914c7 100644
--- a/xfa/fwl/core/ifwl_widget.h
+++ b/xfa/fwl/core/ifwl_widget.h
@@ -11,6 +11,7 @@
 
 #include "core/fxcrt/fx_coordinates.h"
 #include "core/fxcrt/fx_system.h"
+#include "third_party/base/ptr_util.h"
 #include "xfa/fwl/core/cfwl_event.h"
 #include "xfa/fwl/core/cfwl_themepart.h"
 #include "xfa/fwl/core/fwl_widgethit.h"
@@ -112,8 +113,13 @@ class IFWL_Widget {
   virtual IFWL_ThemeProvider* GetThemeProvider();
   virtual FWL_Error SetThemeProvider(IFWL_ThemeProvider* pThemeProvider);
 
-  IFWL_WidgetDelegate* GetCurrentDelegate();
-  void SetCurrentDelegate(IFWL_WidgetDelegate* pDelegate);
+  IFWL_WidgetDelegate* GetDelegate() const { return m_pDelegate.get(); }
+  void SetDelegate(std::unique_ptr<IFWL_WidgetDelegate> delegate) {
+    m_pDelegate = std::move(delegate);
+  }
+  std::unique_ptr<IFWL_WidgetDelegate> ReleaseDelegate() {
+    return pdfium::WrapUnique<IFWL_WidgetDelegate>(m_pDelegate.release());
+  }
 
   const IFWL_App* GetOwnerApp() const;
 
@@ -201,15 +207,9 @@ class IFWL_Widget {
 
   FX_BOOL IsParent(IFWL_Widget* pParent);
 
-  void SetDelegate(std::unique_ptr<IFWL_WidgetDelegate> delegate) {
-    m_pDelegate = std::move(delegate);
-  }
-  IFWL_WidgetDelegate* GetDelegate() const { return m_pDelegate.get(); }
-
   const IFWL_App* const m_pOwnerApp;
   CFWL_WidgetMgr* const m_pWidgetMgr;
   std::unique_ptr<CFWL_WidgetImpProperties> m_pProperties;
-  IFWL_WidgetDelegate* m_pCurDelegate;  // Not owned.
   IFWL_Widget* m_pOuter;
   void* m_pLayoutItem;
   CFWL_Widget* m_pAssociate;