Upgrade in-document custom elements when an element is defined.

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElement.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElement.cpp b/third_party/WebKit/Source/core/dom/custom/CustomElement.cpp
index 4baaeb9fa98f9ce2d5a3a9a18e48369e42cb2d92..12f220e68a603f372f802a8650c12b72121f9725 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElement.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElement.cpp
@@ -5,16 +5,23 @@
 #include "core/dom/custom/CustomElement.h"
 
 #include "core/dom/Document.h"
-#include "core/dom/Element.h"
 #include "core/dom/QualifiedName.h"
 #include "core/dom/custom/V0CustomElement.h"
 #include "core/dom/custom/V0CustomElementRegistrationContext.h"
+#include "core/frame/LocalDOMWindow.h"
 #include "core/html/HTMLElement.h"
 #include "platform/text/Character.h"
 #include "wtf/text/AtomicStringHash.h"
 
 namespace blink {
 
+CustomElementsRegistry* CustomElement::registry(const Element& element)
+{
+    if (LocalDOMWindow* window = element.document().domWindow())
+        return window->customElements();
+    return nullptr;
+}
+
 bool CustomElement::isValidName(const AtomicString& name)
 {
     if (!name.length() || name[0] < 'a' || name[0] > 'z')