Convert legacy 'native code' to JS-forms in dart:html

lib/html/src/dart2js_IDBKeyRangeFactoryProvider.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.
 
 class _IDBKeyRangeFactoryProvider {
 
   static IDBKeyRange createIDBKeyRange_only(/*IDBKey*/ value) =>
       _only(_class(), _translateKey(value));
 
   static IDBKeyRange createIDBKeyRange_lowerBound(
       /*IDBKey*/ bound, [bool open = false]) =>
       _lowerBound(_class(), _translateKey(bound), open);
 
   static IDBKeyRange createIDBKeyRange_upperBound(
       /*IDBKey*/ bound, [bool open = false]) =>
       _upperBound(_class(), _translateKey(bound), open);
 
   static IDBKeyRange createIDBKeyRange_bound(/*IDBKey*/ lower, /*IDBKey*/ upper,
       [bool lowerOpen = false, bool upperOpen = false]) =>
       _bound(_class(), _translateKey(lower), _translateKey(upper),
              lowerOpen, upperOpen);
 
   static var _cachedClass;
 
   static _class() {
     if (_cachedClass != null) return _cachedClass;
     return _cachedClass = _uncachedClass();
   }
 
-  static _uncachedClass() native '''
-      return window.webkitIDBKeyRange || window.mozIDBKeyRange ||
-             window.msIDBKeyRange || window.IDBKeyRange;
-  ''';
+  static _uncachedClass() =>
+    JS('var',
+       '''window.webkitIDBKeyRange || window.mozIDBKeyRange ||
+          window.msIDBKeyRange || window.IDBKeyRange''');
 
   static _translateKey(idbkey) => idbkey;  // TODO: fixme.
 
-  static _IDBKeyRangeImpl _only(cls, value) native
-      '''return cls.only(value);''';
+  static _IDBKeyRangeImpl _only(cls, value) =>
+       JS('_IDBKeyRangeImpl', '#.only(#)', cls, value);
 
-  static _IDBKeyRangeImpl _lowerBound(cls, bound, open) native
-      '''return cls.lowerBound(bound, open);''';
+  static _IDBKeyRangeImpl _lowerBound(cls, bound, open) =>
+       JS('_IDBKeyRangeImpl', '#.lowerBound(#, #)', cls, bound, open);
 
-  static _IDBKeyRangeImpl _upperBound(cls, bound, open) native
-      '''return cls.upperBound(bound, open);''';
+  static _IDBKeyRangeImpl _upperBound(cls, bound, open) =>
+       JS('_IDBKeyRangeImpl', '#.upperBound(#, #)', cls, bound, open);
 
-  static _IDBKeyRangeImpl _bound(cls, lower, upper, lowerOpen, upperOpen) native
-      '''return cls.bound(lower, upper, lowerOpen, upperOpen);''';
-
+  static _IDBKeyRangeImpl _bound(cls, lower, upper, lowerOpen, upperOpen) =>
+       JS('_IDBKeyRangeImpl', '#.bound(#, #, #, #)',
+          cls, lower, upper, lowerOpen, upperOpen);
 }