Revert "Failure from a few days ago (returning null) on an exception masked error"

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 103 matching lines @@
 wrap_jso(jsObject) {
   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 && wrapper is! js.JsObject) {
+    if (wrapper != null) {
       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 237 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;
 }