Removed Polymer from Observatory deps

packages/polymer_interop/lib/src/build/replace_polymer_js.dart

-// Copyright (c) 2014, 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.
-library polymer_interop.src.build.replace_polymer_js.dart;
-
-import 'dart:async';
-import 'package:barback/barback.dart';
-
-/// Replaces `polymer.min.js` with `polymer.js` in development mode.
-class ReplacePolymerJsTransformer extends Transformer {
-  BarbackSettings settings;
-
-  ReplacePolymerJsTransformer.asPlugin(this.settings);
-
-  bool isPrimary(AssetId id) {
-    if (settings.mode == BarbackMode.RELEASE) return false;
-    return id.path == 'lib/src/js/polymer.html';
-  }
-
-  Future apply(Transform transform) async {
-    var contents = await transform.primaryInput.readAsString();
-    contents = contents.replaceFirst('polymer.min.js', 'polymer.js');
-    transform
-        .addOutput(new Asset.fromString(transform.primaryInput.id, contents));
-  }
-}