Revert "Build Observatory with runtime"

runtime/bin/vmservice/observatory/lib/src/app/target_manager.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.
 
 part of app;
 
 class ChromiumTargetLister {
   /// Fetch the list of chromium [NetworkVMTargets].
   static Future<List<WebSocketVMTarget>> fetch(String networkAddress) {
     if (networkAddress == null) {
@@ skipping 110 matching lines @@
     if (loaded == null) {
       return;
     }
     for (var i = 0; i < loaded.length; i++) {
       loaded[i] = new WebSocketVMTarget.fromMap(loaded[i]);
     }
     this.history.addAll(loaded);
     _sort();
   }
 }