Fixed improper construction of custom elements.

sdk/lib/html/html_common/conversions_dartium.dart

 part of html_common;
 
 convertDartToNative_PrepareForStructuredClone(value) =>
     new _StructuredCloneDartium().convertDartToNative_PrepareForStructuredClone(value);
 
 convertNativeToDart_AcceptStructuredClone(object, {mustCopy: false}) =>
     new _AcceptStructuredCloneDartium().convertNativeToDart_AcceptStructuredClone(object, mustCopy: mustCopy);
 
 class _StructuredCloneDartium extends _StructuredClone {
   newJsMap() => new js.JsObject(js.context["Object"]);
@@ skipping 104 matching lines @@
   try {
     if (jsObject is! js.JsObject || jsObject == null) {
       // JS Interop converted the object to a Dart class e.g., Uint8ClampedList.
       // or it's a simple type.
       return jsObject;
     }
 
     var wrapper = js.getDartHtmlWrapperFor(jsObject);
     // if we have a wrapper return the Dart instance.
     if (wrapper != null) {
-      var customElementClass = getCustomElementType(wrapper.blink_jsObject);
-      if (wrapper.runtimeType != customElementClass && customElementClass != null) {
-        if (wrapper.runtimeType == HtmlElement && !wrapper.isBadUpgrade) {
-          // We're a Dart instance if it's HtmlElement and we have a customElement
-          // class then we need to upgrade.
-          if (customElementClass != null) {
-            var dartClass_instance;
-            try {
-              dartClass_instance = _blink.Blink_Utils.constructElement(customElementClass, jsObject);
-            } finally {
-              dartClass_instance.blink_jsObject = jsObject;
-              return dartClass_instance;
-            }
-          }
-        }
-      }
-
       return wrapper;
     }
 
     if (jsObject is js.JsArray) {
       var wrappingList = new DartHtmlWrappingList(jsObject);
       js.setDartHtmlWrapperFor(jsObject, wrappingList);
       return wrappingList;
     }
 
     // Try the most general type conversions on it.
@@ skipping 21 matching lines @@
 
     var dartClass_instance;
     var customElementClass = null;
     var extendsTag = "";
     var custom = getCustomElementEntry(jsObject);
     if (custom != null) {
       customElementClass = custom['type'];
       extendsTag = custom['extends'];
     }
 
-    // Custom Element to upgrade.
-    // Only allow custome elements to be created in the html or svg default
+    // Only allow custom elements to be created in the html or svg default
     // namespace.
+    var func;
     var defaultNS = jsObject['namespaceURI'] == 'http://www.w3.org/1999/xhtml' ||
         jsObject['namespaceURI'] ==  'http://www.w3.org/2000/svg';
     if (customElementClass != null && extendsTag == "" && defaultNS) {
-      try {
-        dartClass_instance = _blink.Blink_Utils.constructElement(customElementClass, jsObject);
-      } finally {
-        dartClass_instance.blink_jsObject = jsObject;
-        js.setDartHtmlWrapperFor(jsObject, dartClass_instance);
-     }
+      // The customElementClass is known but we can't create the real class so
+      // create the HtmlElement and it will get upgraded when registerElement's
+      // createdCallback is called.
+      func = getHtmlCreateFunction('HTMLElement');
     } else {
-      var func = getHtmlCreateFunction(jsTypeName);
+      func = getHtmlCreateFunction(jsTypeName);
       if (func == null) {
         if (jsTypeName == 'auto-binding') {
-          func = getHtmlCreateFunction("HTMLTemplateElement");
+          func = getHtmlCreateFunction('HTMLTemplateElement');
         } else if (jsObject.toString() == "[object HTMLElement]") {
           // One last ditch effort could be a JS custom element.
-          func = getHtmlCreateFunction("HTMLElement");
+          func = getHtmlCreateFunction('HTMLElement');
         }
       }
-      if (func != null) {
-        dartClass_instance = func();
-        dartClass_instance.blink_jsObject = jsObject;
-        js.setDartHtmlWrapperFor(jsObject, dartClass_instance);
-      }
     }
 
+    // Can we construct a Dart class?
+    if (func != null) {
+      dartClass_instance = func();
+
+      // Wrap our Dart instance in both directions.
+      dartClass_instance.blink_jsObject = jsObject;
+      js.setDartHtmlWrapperFor(jsObject, dartClass_instance);
+    }
+
     // TODO(jacobr): cache that this is not a dart:html JS class.
     return dartClass_instance;
   } catch(e, stacktrace){
     if (interop_checks) {
       if (e is DebugAssertException)
         window.console.log("${e.message}\n ${stacktrace}");
       else
         window.console.log("${stacktrace}");
     }
   }
@@ skipping 165 matching lines @@
 
   final js.JsArray blink_jsObject;
 
   operator [](int index) => wrap_jso(js.JsNative.getArrayIndex(blink_jsObject, index));
 
   operator []=(int index, value) => blink_jsObject[index] = value;
 
   int get length => blink_jsObject.length;
   int set length(int newLength) => blink_jsObject.length = newLength;
 }