Make custom elements work in HTML imports

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp b/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp
index a9e7d5cd80b3ae9db6a1ff58feab377d277472db..db82d7bbadc7ea20a9d938449f7c0f39c7d5e6be 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp
@@ -55,8 +55,10 @@ static String errorMessageForConstructorResult(Element* element,
     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

[dominicc (has gone to gerrit), 2016/08/22 12:05:58]

(Still wondering about this.)

[kochi, 2016/08/22 15:56:30]

I figured out.

The v8 createElement binding always passes window->document for HTMLConstructor:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/bindings/core/...

So here element->document() gets always window.document, even for
importDoc->createElement().
I'll work on the fix.

+        && 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";