Fix all Observatory warnings/errors.

runtime/observatory/lib/src/elements/heap_profile.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 heap_profile_element;
 
 import 'dart:html';
 import 'observatory_element.dart';
-import 'package:logging/logging.dart';
 import 'package:observatory/app.dart';
 import 'package:observatory/service.dart';
 import 'package:observatory/elements.dart';
 import 'package:polymer/polymer.dart';
 
 class ClassSortedTable extends SortedTable {
 
   ClassSortedTable(columns) : super(columns);
 
   @override
@@ skipping 339 matching lines @@
   }
 
   @observable String formattedTotalCollectionTime(bool newSpace) {
     if (profile == null) {
       return '';
     }
     var heap = newSpace ? isolate.newSpace : isolate.oldSpace;
     return '${Utils.formatSeconds(heap.totalCollectionTimeInSeconds)} secs';
   }
 }