Clear analyzer warning on Observatory

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

 // Copyright (c) 2016, 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.
 
 import 'dart:html';
 import 'dart:async';
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/src/elements/cpu_profile/virtual_tree.dart';
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 import 'package:observatory/src/elements/sample_buffer_control.dart';
 import 'package:observatory/src/elements/stack_trace_tree_config.dart';
 
 class ClassAllocationProfileElement extends HtmlElement implements Renderable {
   static const tag = const Tag<ClassAllocationProfileElement>(
       'class-allocation-profile',
       dependencies: const [
         SampleBufferControlElement.tag,
         StackTraceTreeConfigElement.tag,
         CpuProfileVirtualTreeElement.tag,
       ]);
 
   RenderingScheduler<ClassAllocationProfileElement> _r;
 
   Stream<RenderedEvent<ClassAllocationProfileElement>> get onRendered =>
       _r.onRendered;
 
+  M.VM _vm;
   M.IsolateRef _isolate;
   M.Class _cls;
   M.ClassSampleProfileRepository _profiles;
   Stream<M.SampleProfileLoadingProgressEvent> _progressStream;
   M.SampleProfileLoadingProgress _progress;
   M.SampleProfileTag _tag = M.SampleProfileTag.none;
   ProfileTreeMode _mode = ProfileTreeMode.function;
   M.ProfileTreeDirection _direction = M.ProfileTreeDirection.exclusive;
 
   M.IsolateRef get isolate => _isolate;
   M.Class get cls => _cls;
 
-  factory ClassAllocationProfileElement(M.IsolateRef isolate, M.Class cls,
-      M.ClassSampleProfileRepository profiles,
+  factory ClassAllocationProfileElement(M.VM vm, M.IsolateRef isolate,
+      M.Class cls, M.ClassSampleProfileRepository profiles,
       {RenderingQueue queue}) {
+    assert(vm != null);
     assert(isolate != null);
     assert(cls != null);
     assert(profiles != null);
     ClassAllocationProfileElement e = document.createElement(tag.name);
     e._r = new RenderingScheduler(e, queue: queue);
+    e._vm = vm;
     e._isolate = isolate;
     e._cls = cls;
     e._profiles = profiles;
     return e;
   }
 
   ClassAllocationProfileElement.created() : super.created();
 
   @override
   void attached() {
     super.attached();
     _r.enable();
     _request();
   }
 
   @override
   void detached() {
     super.detached();
     children = [];
     _r.disable(notify: true);
   }
 
   void render() {
     if (_progress == null) {
       children = const [];
       return;
     }
     final content = [
-      new SampleBufferControlElement(isolate.vm, _progress, _progressStream,
+      new SampleBufferControlElement(_vm, _progress, _progressStream,
           selectedTag: _tag, queue: _r.queue)
         ..onTagChange.listen((e) {
           _tag = e.element.selectedTag;
           _request(forceFetch: true);
         })
     ];
     if (_progress.status == M.SampleProfileLoadingStatus.loaded) {
       CpuProfileVirtualTreeElement tree;
       content.addAll([
         new BRElement(),
         new StackTraceTreeConfigElement(
             mode: _mode,
             direction: _direction,
             showFilter: false,
             queue: _r.queue)
           ..onModeChange.listen((e) {
             _mode = tree.mode = e.element.mode;
           })
           ..onDirectionChange.listen((e) {
             _direction = tree.direction = e.element.direction;
           }),
         new BRElement(),
         tree = new CpuProfileVirtualTreeElement(_isolate, _progress.profile,
             queue: _r.queue)
       ]);
     }
     children = content;
   }
 
-  Future _request() async {
+  Future _request({bool forceFetch: false}) async {
     _progress = null;
-    _progressStream = _profiles.get(_isolate, _cls, _tag);
+    _progressStream =
+        _profiles.get(_isolate, _cls, _tag, forceFetch: forceFetch);
     _r.dirty();
     _progress = (await _progressStream.first).progress;
     _r.dirty();
     if (M.isSampleProcessRunning(_progress.status)) {
       _progress = (await _progressStream.last).progress;
       _r.dirty();
     }
   }
 }