Make Custom Elements V1 work in HTML imports documents

third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp

 // 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.
 
 #include "core/dom/custom/CustomElementDefinition.h"
 
 #include "core/dom/Attr.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/custom/CustomElement.h"
 #include "core/dom/custom/CustomElementAttributeChangedCallbackReaction.h"
@@ skipping 34 matching lines @@
     // 6.1.4. If result's attribute list is not empty, then throw a NotSupportedError.
     if (element->hasAttributes())
         return "The result must not have attributes";
     // 6.1.5. If result has children, then throw a NotSupportedError.
     if (element->hasChildren())
         return "The result must not have children";
     // 6.1.6. If result's parent is not null, then throw a NotSupportedError.
     if (element->parentNode())
         return "The result must not have a parent";
     // 6.1.7. If result's node document is not document, then throw a NotSupportedError.
-    if (&element->document() != &document)
+    if (&element->document() != &document
+        && element->document().contextDocument() != document.contextDocument()) {
         return "The result must be in the same document";
+    }
     // 6.1.8. If result's namespace is not the HTML namespace, then throw a NotSupportedError.
     if (element->namespaceURI() != HTMLNames::xhtmlNamespaceURI)
         return "The result must have HTML namespace";
     // 6.1.9. If result's local name is not equal to localName, then throw a NotSupportedError.
     if (element->localName() != tagName.localName())
         return "The result must have the same localName";
     return String();
 }
 
 void CustomElementDefinition::checkConstructorResult(Element* element,
@@ skipping 102 matching lines @@
         element->synchronizeAttribute(name);
     for (const auto& attribute : element->attributesWithoutUpdate()) {
         if (hasAttributeChangedCallback(attribute.name())) {
             enqueueAttributeChangedCallback(element, attribute.name(),
                 nullAtom, attribute.value());
         }
     }
 }
 
 } // namespace blink