Add "Failed" custom element state

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 9d2d0e45eb3dc2543e010c2ef4a6a85d5b5e42ac..d6110c5fecba8c536245720a9fe4cd74a05d9ec1 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -1915,6 +1915,11 @@ void Element::setNeedsCompositingUpdate()
     layoutObject->layer()->updateSelfPaintingLayer();
 }
 
+bool Element::isDefined() const
+{
+    return CustomElement::isDefined(getCustomElementState());

[dominicc (has gone to gerrit), 2016/07/26 05:47:42]

Do we need CustomElement::isDefined and Element::isDefined? Is there any place
where we're *just* testing a state and not an element's state?

+}
+
 void Element::setCustomElementDefinition(V0CustomElementDefinition* definition)
 {
     if (!hasRareData() && !definition)
@@ -1959,7 +1964,7 @@ ShadowRoot* Element::attachShadow(const ScriptState* scriptState, const ShadowRo
 
     const AtomicString& tagName = localName();
     bool tagNameIsSupported = isV0CustomElement()
-        || isCustomElement()
+        || getCustomElementState() != CustomElementState::Uncustomized
         || tagName == HTMLNames::articleTag
         || tagName == HTMLNames::asideTag
         || tagName == HTMLNames::blockquoteTag