[Layout API] Create api/LayoutLIItem and use it in html/HTMLLIElement

third_party/WebKit/Source/core/layout/api/LayoutItem.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef LayoutItem_h
 #define LayoutItem_h
 
 #include "core/inspector/InspectorTraceEvents.h"
 #include "core/layout/LayoutObject.h"
 #include "wtf/Allocator.h"
@@ skipping 71 matching lines @@
     bool isImage() const
     {
         return m_layoutObject->isImage();
     }
 
     bool isLayoutFullScreen() const
     {
         return m_layoutObject->isLayoutFullScreen();
     }
 
+    bool isListItem() const
+    {
+        return m_layoutObject->isListItem();
+    }
+
     bool needsLayout()
     {
         return m_layoutObject->needsLayout();
     }
 
     void layout()
     {
         m_layoutObject->layout();
     }
 
@@ skipping 46 matching lines @@
     LayoutObject* layoutObject() { return m_layoutObject; }
     const LayoutObject* layoutObject() const { return m_layoutObject; }
 
 private:
     LayoutObject* m_layoutObject;
 };
 
 } // namespace blink
 
 #endif // LayoutItem_h