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

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElement.h
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElement.h b/third_party/WebKit/Source/core/dom/custom/CustomElement.h
index 7b9dcccc3921ced551871506c108def492927dc4..92e8304a085cdc87b4e9156e272a8d4aeca1443c 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElement.h
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElement.h
@@ -6,7 +6,8 @@
 #define CustomElement_h
 
 #include "core/CoreExport.h"
-#include "core/dom/Document.h"
+#include "core/HTMLNames.h"
+#include "core/dom/Element.h"
 #include "wtf/Allocator.h"
 #include "wtf/text/AtomicString.h"
 
@@ -15,10 +16,36 @@ namespace blink {
 class Document;
 class HTMLElement;
 class QualifiedName;
+class CustomElementRegistry;
 
 class CORE_EXPORT CustomElement {
     STATIC_ONLY(CustomElement);
 public:
+    // Retrieves the CustomElementsRegistry for Element, if any. This
+    // may be a different object for a given element over its lifetime
+    // as it moves between documents.
+    static CustomElementsRegistry* registry(const Element&);
+
+    // Returns true if element could possibly match a custom element
+    // descriptor *now*. See CustomElementDescriptor::matches for the
+    // meaning of "match". Custom element processing which depends on
+    // matching a descriptor, such as upgrade, can be skipped for
+    // elements that fail this test.
+    //
+    // Although this result is currently constant for a given element,
+    // when customized built-in elements are implemented the result
+    // will depend on the value of the 'is' attribute. In addition,
+    // these elements may stop matching descriptors after being
+    // upgraded, so use Node::getCustomElementState to detect
+    // customized elements.
+    static bool descriptorMayMatch(const Element& element)
+    {
+        // TODO(dominicc): Broaden this check when customized built-in
+        // elements are implemented.
+        return isValidName(element.localName())
+            && element.namespaceURI() == HTMLNames::xhtmlNamespaceURI;
+    }
+
     static bool isValidName(const AtomicString& name);
 
     static bool shouldCreateCustomElement(Document&, const AtomicString& localName);