Remove CFWL_WidgetMrg::SetOwner().

Its last caller was removed way back in
  https://pdfium-review.googlesource.com/c/pdfium/+/49410

because it was also uncalled.

Change-Id: I459c1558a8523f61e0012d9ea2a42799937eaf34
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/72612
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

xfa/fwl/cfwl_widgetmgr.cpp

diff --git a/xfa/fwl/cfwl_widgetmgr.cpp b/xfa/fwl/cfwl_widgetmgr.cpp
index 3549127..bd9afd0 100644
--- a/xfa/fwl/cfwl_widgetmgr.cpp
+++ b/xfa/fwl/cfwl_widgetmgr.cpp
@@ -199,25 +199,6 @@
   m_mapWidgetItem.erase(pWidget);
 }
 
-void CFWL_WidgetMgr::SetOwner(CFWL_Widget* pOwner, CFWL_Widget* pOwned) {
-  Item* pParentItem = GetWidgetMgrItem(pOwner);
-  if (!pParentItem) {
-    auto item = std::make_unique<Item>(pOwner);
-    pParentItem = item.get();
-    m_mapWidgetItem[pOwner] = std::move(item);
-
-    pParentItem->pParent = GetWidgetMgrItem(nullptr);
-    AppendWidget(pOwner);
-  }
-
-  Item* pItem = GetWidgetMgrItem(pOwned);
-  if (!pItem) {
-    auto item = std::make_unique<Item>(pOwned);
-    pItem = item.get();
-    m_mapWidgetItem[pOwned] = std::move(item);
-  }
-  pItem->pOwner = pParentItem;
-}
 void CFWL_WidgetMgr::SetParent(CFWL_Widget* pParent, CFWL_Widget* pChild) {
   Item* pParentItem = GetWidgetMgrItem(pParent);
   Item* pItem = GetWidgetMgrItem(pChild);

xfa/fwl/cfwl_widgetmgr.h

diff --git a/xfa/fwl/cfwl_widgetmgr.h b/xfa/fwl/cfwl_widgetmgr.h
index 1f65037..59f5751 100644
--- a/xfa/fwl/cfwl_widgetmgr.h
+++ b/xfa/fwl/cfwl_widgetmgr.h
@@ -51,7 +51,6 @@
 
   void InsertWidget(CFWL_Widget* pParent, CFWL_Widget* pChild);
   void RemoveWidget(CFWL_Widget* pWidget);
-  void SetOwner(CFWL_Widget* pOwner, CFWL_Widget* pOwned);
   void SetParent(CFWL_Widget* pParent, CFWL_Widget* pChild);
 
   CFWL_Widget* GetWidgetAtPoint(CFWL_Widget* pParent,