Removed Polymer from Observatory deps

packages/js/lib/js.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.
-
-/// Allows interoperability with Javascript APIs.
-library js;
-
-export 'dart:js' show allowInterop, allowInteropCaptureThis;
-
-/// A metadata annotation that indicates that a Library, Class, or member is
-/// implemented directly in JavaScript. All external members of a class or
-/// library with this annotation implicitly have it as well.
-///
-/// Specifying [name] customizes the JavaScript name to use. By default the
-/// dart name is used. It is not valid to specify a custom [name] for class
-/// instance members.
-class JS {
-  final String name;
-  const JS([this.name]);
-}
-
-class _Anonymous {
-  const _Anonymous();
-}
-
-/// A metadata annotation that indicates that a @JS annotated class is
-/// structural and does not have a known JavaScript prototype.
-///
-/// Factory constructors for anonymous JavaScript classes desugar to creating
-/// JavaScript object literals with name-value pairs corresponding to the
-/// parameter names and values.
-const _Anonymous anonymous = const _Anonymous();