Add AsLayoutItem()/ToLayoutItem() functions.

xfa/src/fxfa/src/parser/xfa_layout_appadapter.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef _XFA_LAYOUT_APPADAPTER_H_
 #define _XFA_LAYOUT_APPADAPTER_H_
 class CXFA_TraverseStrategy_PageAreaContainerLayoutItem {
  public:
@@ skipping 12 matching lines @@
       CXFA_ContainerLayoutItem* pLayoutItem) {
     return (CXFA_ContainerLayoutItem*)pLayoutItem->m_pParent;
   }
 };
 class CXFA_TraverseStrategy_ContentAreaContainerLayoutItem {
  public:
   static inline CXFA_ContainerLayoutItem* GetFirstChild(
       CXFA_ContainerLayoutItem* pLayoutItem) {
     for (CXFA_LayoutItem* pChildItem = pLayoutItem->m_pFirstChild; pChildItem;
          pChildItem = pChildItem->m_pNextSibling) {
-      if (pChildItem->IsContentLayoutItem()) {
-        continue;
+      if (CXFA_ContainerLayoutItem* pContainer =
+              pChildItem->AsContainerLayoutItem()) {
+        return pContainer;
       }
-      return (CXFA_ContainerLayoutItem*)pChildItem;
     }
-    return NULL;
+    return nullptr;
   }
   static inline CXFA_ContainerLayoutItem* GetNextSibling(
       CXFA_ContainerLayoutItem* pLayoutItem) {
     for (CXFA_LayoutItem* pChildItem = pLayoutItem->m_pNextSibling; pChildItem;
          pChildItem = pChildItem->m_pNextSibling) {
-      if (pChildItem->IsContentLayoutItem()) {
-        continue;
+      if (CXFA_ContainerLayoutItem* pContainer =
+              pChildItem->AsContainerLayoutItem()) {
+        return pContainer;
       }
-      return (CXFA_ContainerLayoutItem*)pChildItem;
     }
-    return NULL;
+    return nullptr;
   }
   static inline CXFA_ContainerLayoutItem* GetParent(
       CXFA_ContainerLayoutItem* pLayoutItem) {
     return (CXFA_ContainerLayoutItem*)pLayoutItem->m_pParent;
   }
 };
 class CXFA_TraverseStrategy_ContentLayoutItem {
  public:
   static inline CXFA_ContentLayoutItem* GetFirstChild(
       CXFA_ContentLayoutItem* pLayoutItem) {
     return (CXFA_ContentLayoutItem*)pLayoutItem->m_pFirstChild;
   }
   static inline CXFA_ContentLayoutItem* GetNextSibling(
       CXFA_ContentLayoutItem* pLayoutItem) {
     return (CXFA_ContentLayoutItem*)pLayoutItem->m_pNextSibling;
   }
   static inline CXFA_ContentLayoutItem* GetParent(
       CXFA_ContentLayoutItem* pLayoutItem) {
     return (CXFA_ContentLayoutItem*)pLayoutItem->m_pParent;
   }
 };
 FX_DWORD XFA_GetRelevant(CXFA_Node* pFormItem, FX_DWORD dwParentRelvant);
 void XFA_ReleaseLayoutItem(CXFA_LayoutItem* pLayoutItem);
 #endif