Change IFWL_Widget to store a single delegate.

xfa/fwl/core/cfwl_widget.cpp

Index: xfa/fwl/core/cfwl_widget.cpp
diff --git a/xfa/fwl/core/cfwl_widget.cpp b/xfa/fwl/core/cfwl_widget.cpp
index 999a5a8443a2e03bbe449b23900b54eec8abb317..d0e2df88d0b2891fc2dcd0ed1d3bc75dc03b8ef1 100644
--- a/xfa/fwl/core/cfwl_widget.cpp
+++ b/xfa/fwl/core/cfwl_widget.cpp
@@ -127,11 +127,11 @@ FWL_Error CFWL_Widget::DrawWidget(CFX_Graphics* pGraphics,
   return m_pIface->DrawWidget(pGraphics, pMatrix);
 }
 
-IFWL_WidgetDelegate* CFWL_Widget::GetCurrentDelegate() {
-  return m_pIface ? m_pIface->GetCurrentDelegate() : nullptr;
+std::unique_ptr<IFWL_WidgetDelegate> CFWL_Widget::ReleaseDelegate() {
+  return m_pIface ? m_pIface->ReleaseDelegate() : nullptr;
 }
 
-void CFWL_Widget::SetCurrentDelegate(IFWL_WidgetDelegate* pDelegate) {
+void CFWL_Widget::SetDelegate(std::unique_ptr<IFWL_WidgetDelegate> pDelegate) {
   if (m_pIface)
-    m_pIface->SetCurrentDelegate(pDelegate);
+    m_pIface->SetDelegate(std::move(pDelegate));
 }