Removed DARTIUM codegen for IDLS (sdk/lib/dartium)

tools/dom/templates/html/impl/impl_DataTransferItemList.darttemplate

 // Copyright (c) 2013, 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 $LIBRARYNAME;
 
 @DocsEditable()
 $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$MIXINS$IMPLEMENTS {
 $!MEMBERS
 
   DataTransferItem operator[] (int index) {
-$if DART2JS
     return JS('DataTransferItem', '#[#]', this, index);
-$else
-    // TODO(alanknight): I think that all the __getter__ generators should just
-    // do property access, but that's major surgery. This one is a problem, so
-    // just hard-code it for now.
-    return _blink.Blink_JsNative_DomException.getProperty(this, index.toString());
-$endif
   }
 
 }