fix #30030, fix #27327 - fix tearoffs and various Object member bugs

pkg/dev_compiler/lib/src/compiler/js_interop.dart

 // Copyright (c) 2015, 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.
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/dart/element/element.dart';
 
 import 'element_helpers.dart';
 
@@ skipping 56 matching lines @@
 bool isJsPeerInterface(DartObjectImpl value) =>
     _isBuiltinAnnotation(value, '_js_helper', 'JsPeerInterface');
 
 bool isNativeAnnotation(DartObjectImpl value) =>
     _isBuiltinAnnotation(value, '_js_helper', 'Native');
 
 /// Returns the name value of the `JSExportName` annotation (when compiling
 /// the SDK), or `null` if there's none. This is used to control the name
 /// under which functions are compiled and exported.
 String getJSExportName(Element e) {
-  var original = e;
-  if (original is PropertyAccessorElement) e = original.variable;
-  if (e.source.isInSystemLibrary) {
-    var real = original.isSynthetic ? e : original;
-    return getAnnotationName(real, isJSExportNameAnnotation) ?? e.name;
-  }
-  return e.name;
+  if (!e.source.isInSystemLibrary) return null;
+
+  e = e is PropertyAccessorElement && e.isSynthetic ? e.variable : e;
+  return getAnnotationName(e, isJSExportNameAnnotation);
 }