Re-apply "Adding a mechanism to 'upgrade' the Dart type of elements"

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 _ConsoleVariables {
   Map<String, Object> _data = new Map<String, Object>();
 
   /**
@@ skipping 378 matching lines @@
 
   static String addTrailingDot(String str) => '${str}.';
 
   static String demangle(String str) {
     var atPos = str.indexOf('@');
     return atPos == -1 ? str : str.substring(0, atPos);
   }
 
   static bool isNoSuchMethodError(obj) => obj is NoSuchMethodError;
 
-  static bool _isBuiltinType(ClassMirror cls) {
-    // TODO(vsm): Find a less hackish way to do this.
-    LibraryMirror lib = cls.owner;
-    String libName = lib.uri.toString();
-    return libName.startsWith('dart:');
-  }
-
   static void register(Document document, String tag, Type type,
       String extendsTagName) {
-    // TODO(vsm): Move these checks into native code.
-    ClassMirror cls = reflectClass(type);
-    if (_isBuiltinType(cls)) {
-      throw new UnsupportedError("Invalid custom element from ${(cls.owner as LibraryMirror).uri}.");
-    }
-    var className = MirrorSystem.getName(cls.simpleName);
-    var createdConstructor = cls.declarations[new Symbol('$className.created')];
-    if (createdConstructor == null ||
-        createdConstructor is! MethodMirror ||
-        !createdConstructor.isConstructor) {
-      throw new UnsupportedError(
-          'Class is missing constructor $className.created');
-    }
+    var nativeClass = _validateCustomType(type);
 
-    if (createdConstructor.parameters.length > 0) {
-      throw new UnsupportedError(
-          'Constructor $className.created must take zero arguments');
-    }
-
-    Symbol objectName = reflectClass(Object).qualifiedName;
-    bool isRoot(ClassMirror cls) =>
-        cls == null || cls.qualifiedName == objectName;
-    Symbol elementName = reflectClass(HtmlElement).qualifiedName;
-    bool isElement(ClassMirror cls) =>
-        cls != null && cls.qualifiedName == elementName;
-    ClassMirror superClass = cls.superclass;
-    ClassMirror nativeClass = _isBuiltinType(superClass) ? superClass : null;
-    while(!isRoot(superClass) && !isElement(superClass)) {
-      superClass = superClass.superclass;
-      if (nativeClass == null && _isBuiltinType(superClass)) {
-        nativeClass = superClass;
-      }
-    }
     if (extendsTagName == null) {
       if (nativeClass.reflectedType != HtmlElement) {
         throw new UnsupportedError('Class must provide extendsTag if base '
             'native class is not HTMLElement');
       }
     }
 
     _register(document, tag, type, extendsTagName);
   }
 
   static void _register(Document document, String tag, Type customType,
       String extendsTagName) native "Utils_register";
 
   static Element createElement(Document document, String tagName) native "Utils_createElement";
 
   static void initializeCustomElement(HtmlElement element) native "Utils_initializeCustomElement";
+
+  static void changeElementWrapper(HtmlElement element, Type type) native "Utils_changeElementWrapper";
 }
 
 class _DOMWindowCrossFrame extends NativeFieldWrapperClass2 implements
     WindowBase {
   _DOMWindowCrossFrame.internal();
 
   // Fields.
   HistoryBase get history native "Window_history_cross_frame_Getter";
   LocationBase get location native "Window_location_cross_frame_Getter";
   bool get closed native "Window_closed_Getter";
@@ skipping 165 matching lines @@
   _scheduleImmediateHelper._schedule(callback);
 };
 
 get _pureIsolateScheduleImmediateClosure => ((void callback()) =>
   throw new UnimplementedError("scheduleMicrotask in background isolates "
                                "are not supported in the browser"));
 
 void _initializeCustomElement(Element e) {
   _Utils.initializeCustomElement(e);
 }