Fix all Observatory warnings/errors.

runtime/observatory/lib/src/elements/cpu_profile.dart

 // 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.
 
 library cpu_profile_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
-import 'package:logging/logging.dart';
 import 'package:observatory/service.dart';
 import 'package:observatory/app.dart';
 import 'package:observatory/cpu_profile.dart';
 import 'package:observatory/elements.dart';
 import 'package:polymer/polymer.dart';
 
 List<String> sorted(Set<String> attributes) {
   var list = attributes.toList();
   list.sort();
   return list;
@@ skipping 583 matching lines @@
       codeTree = new TableTree(tableBody, 2);
     }
     var tree = profile.loadCodeTree(exclusive ? 'exclusive' : 'inclusive');
     if (tree == null) {
       return;
     }
     var rootRow = new CodeProfileTreeRow(codeTree, null, profile, tree.root);
     codeTree.initialize(rootRow);
   }
 }