Sample test for custom elements.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index b5e82af86a71bcc2b997884742fd66c6ae5d288c..494d925d650ba2434513cbdaf9974e62a14162de 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -9635,6 +9635,12 @@ abstract class Element extends Node implements ElementTraversal {
     return e is Element && !(e is UnknownElement);
   }
 
+  /**
+   * Called by the DOM when this element has been instantiated.
+   */
+  @Experimental
+  void onCreated() {}
+
   // Hooks to support custom WebComponents.
   /**
    * Experimental support for [web components][wc]. This field stores a
@@ -13477,6 +13483,17 @@ class HtmlDocument extends Document {
     document.$dom_body = value;
   }
 
+  /**
+   * Registers a custom Element subclass as an available HTML tag.
+   *
+   * Not yet implemented.
+   */
+  @Experimental
+  void register(String tagName, Type elementClass) {
+    // TODO: tagName validation
+    throw new Exception('Not yet implemented');
+  }
+
   @DomName('Document.caretRangeFromPoint')
   Range caretRangeFromPoint(int x, int y) {
     return document.$dom_caretRangeFromPoint(x, y);