vm/service/observatory: Add coverage for functions, some tests, and fix buggy filter

runtime/bin/vmservice/client/lib/src/service/object.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 service;
 
 /// A [ServiceObject] is an object known to the VM service and is tied
 /// to an owning [Isolate].
 abstract class ServiceObject extends Observable {
   static int LexicalSortName(ServiceObject o1, ServiceObject o2) {
@@ skipping 1249 matching lines @@
   static FunctionKind kMethodExtractor = new FunctionKind._internal('method extractor');
   static FunctionKind kNoSuchMethodDispatcher = new FunctionKind._internal('noSuchMethod dispatcher');
   static FunctionKind kInvokeFieldDispatcher = new FunctionKind._internal('invoke field dispatcher');
   static FunctionKind kCollected = new FunctionKind._internal('Collected');
   static FunctionKind kNative = new FunctionKind._internal('Native');
   static FunctionKind kTag = new FunctionKind._internal('Tag');
   static FunctionKind kReused = new FunctionKind._internal('Reused');
   static FunctionKind kUNKNOWN = new FunctionKind._internal('UNKNOWN');
 }
 
-class ServiceFunction extends ServiceObject {
+class ServiceFunction extends ServiceObject with Coverage {
   @observable Class owningClass;
   @observable Library owningLibrary;
   @observable bool isStatic;
   @observable bool isConst;
   @observable ServiceFunction parent;
   @observable Script script;
   @observable int tokenPos;
   @observable int endTokenPos;
   @observable Code code;
   @observable Code unoptimizedCode;
@@ skipping 743 matching lines @@
     var v = list[i];
     if ((v is ObservableMap) && _isServiceMap(v)) {
       list[i] = owner.getFromMap(v);
     } else if (v is ObservableList) {
       _upgradeObservableList(v, owner);
     } else if (v is ObservableMap) {
       _upgradeObservableMap(v, owner);
     }
   }
 }