Restrict the types of nodes that could be assigned to a slot.

third_party/WebKit/Source/core/dom/Node.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004-2011, 2014 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 472 matching lines @@
         return getFlag(InDocumentFlag);
     }
     bool isInShadowTree() const { return getFlag(IsInShadowTreeFlag); }
     bool isInTreeScope() const { return getFlag(static_cast<NodeFlags>(InDocumentFlag | IsInShadowTreeFlag)); }
 
     ElementShadow* parentElementShadow() const;
     bool isInV1ShadowTree() const;
     bool isInV0ShadowTree() const;
     bool isChildOfV1ShadowHost() const;
     bool isChildOfV0ShadowHost() const;
+    bool isSlotAssignable() const { return isTextNode() || isElementNode(); }
 
     bool isDocumentTypeNode() const { return nodeType() == DOCUMENT_TYPE_NODE; }
     virtual bool childTypeAllowed(NodeType) const { return false; }
     unsigned countChildren() const;
 
     bool isDescendantOf(const Node*) const;
     bool contains(const Node*) const;
     bool containsIncludingShadowDOM(const Node*) const;
     bool containsIncludingHostElements(const Node&) const;
     Node* commonAncestor(const Node&, ContainerNode* (*parent)(const Node&)) const;
@@ skipping 424 matching lines @@
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showNode(const blink::Node*);
 void showTree(const blink::Node*);
 void showNodePath(const blink::Node*);
 #endif
 
 #endif // Node_h