Implement the script parts of custom element upgrade steps.

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 4c7626d3171b1e9405d056961fc2d425cf1a3e6d..b261c80514f8de4966a4f07f43eb41362d471fe0 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.cpp
@@ -24,6 +24,11 @@ DEFINE_TRACE(CustomElementDefinition)
 // https://html.spec.whatwg.org/multipage/scripting.html#concept-upgrade-an-element
 void CustomElementDefinition::upgrade(Element* element)
 {
+    // TODO(dominicc): When the attributeChangedCallback is implemented,
+    // enqueue reactions for attributes here.
+    // TODO(dominicc): When the connectedCallback is implemented, enqueue
+    // reactions here, if applicable.
+
     m_constructionStack.append(element);
     size_t depth = m_constructionStack.size();
 
@@ -38,20 +43,7 @@ void CustomElementDefinition::upgrade(Element* element)
     if (!succeeded)
         return;
 
-    // TODO(dominicc): Turn this into an assertion when setting
-    // 'custom' moves to the HTMLElement constructor. We will need to
-    // add a bit for MARQUEE to be custom-gets-callbacks-yet-not-custom.
-    element->setCustomElementState(CustomElementState::Custom);
-
-    // TODO(dominicc): When the attributeChangedCallback is implemented,
-    // enqueue reactions for attributes here.
-    // TODO(dominicc): When the connectedCallback is implemented, enqueue
-    // reactions here, if applicable.
-}
-
-bool CustomElementDefinition::runConstructor(Element*)
-{
-    return true;
+    CHECK(element->getCustomElementState() == CustomElementState::Custom);
 }
 
 } // namespace blink