Initial Dartium custom element support

tools/dom/src/native_DOMImplementation.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of html;
 
 class _Utils {
   static double dateTimeToDouble(DateTime dateTime) =>
       dateTime.millisecondsSinceEpoch.toDouble();
   static DateTime doubleToDateTime(double dateTime) {
@@ skipping 176 matching lines @@
   static String stripTrailingDot(String str) =>
     (str != null && str[str.length - 1] == '.') ? str.substring(0, str.length - 1) : str;
 
   static String addTrailingDot(String str) => '${str}.';
 
   static bool isNoSuchMethodError(obj) => obj is NoSuchMethodError;
 
   // TODO(jacobr): we need a failsafe way to determine that a Node is really a
   // DOM node rather than just a class that extends Node.
   static bool isNode(obj) => obj is Node;
+
+  static void register(String tag, Type type) {
+    // TODO(vsm): Move these checks into native code.
+    if (type == null) {
+      throw new UnsupportedError("Invalid null type.");
+    }
+    ClassMirror cls = reflectClass(type);
+    LibraryMirror lib = cls.owner;
+    String libName = lib.uri.toString();
+    if (libName.startsWith('dart:')) {
+      throw new UnsupportedError("Invalid custom element from $libName.");
+    }
+    ClassMirror superClass = cls.superclass;
+
+    Symbol objectName = reflectClass(Object).qualifiedName;
+    bool isRoot(ClassMirror cls) =>
+      cls == null || cls.qualifiedName == objectName;
+    Symbol elementName = reflectClass(Element).qualifiedName;
+    bool isElement(ClassMirror cls) =>
+      cls != null && cls.qualifiedName == elementName;
+
+    while(!isRoot(superClass) && !isElement(superClass)) {
+      superClass = superClass.superclass;
+    }
+
+    if (isRoot(superClass)) {
+      throw new UnsupportedError("Invalid custom element doesn't inherit from Element.");
+    }
+    _register(tag, type);
+  }
+
+  static void _register(String tag, Type type) native "Utils_register";
 }
 
 class _NPObject extends NativeFieldWrapperClass1 {
   _NPObject.internal();
   static _NPObject retrieve(String key) native "NPObject_retrieve";
   property(String propertyName) native "NPObject_property";
   invoke(String methodName, [List args = null]) native "NPObject_invoke";
 }
 
 class _DOMWindowCrossFrame extends NativeFieldWrapperClass1 implements
@@ skipping 181 matching lines @@
   _send(msg) {
     _sendToHelperIsolate(msg, _sendPort);
   }
 
   bool get isActive => _isActive;
 }
 
 get _pureIsolateTimerFactoryClosure =>
     ((int milliSeconds, void callback(Timer time), bool repeating) =>
         new _PureIsolateTimer(milliSeconds, callback, repeating));