Converted Observatory heap-snapshot element

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

 // Copyright (c) 2015, 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_snapshot_element;
+// 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.
 
 import 'dart:async';
 import 'dart:html';
-import 'class_ref_wrapper.dart';
-import 'observatory_element.dart';
-import 'package:observatory/app.dart';
-import 'package:observatory/service.dart';
-import 'package:observatory/elements.dart';
-import 'package:observatory/object_graph.dart';
-import 'package:polymer/polymer.dart';
-import 'package:logging/logging.dart';
-
-class DominatorTreeRow extends TableTreeRow {
-  final ObjectVertex vertex;
-  final HeapSnapshot snapshot;
-
-  var _domTreeChildren;
-  get domTreeChildren {
-    if (_domTreeChildren == null) {
-      _domTreeChildren = vertex.dominatorTreeChildren();
-    }
-    return _domTreeChildren;
-  }
-
-  DominatorTreeRow(TableTree tree,
-                   TableTreeRow parent,
-                   this.vertex,
-                   this.snapshot)
-      : super(tree, parent) {
-  }
-
-  bool hasChildren() {
-    return domTreeChildren.length > 0;
+import 'dart:math' as Math;
+import 'package:observatory/models.dart' as M;
+import 'package:observatory/src/elements/class_ref.dart';
+import 'package:observatory/src/elements/containers/virtual_tree.dart';
+import 'package:observatory/src/elements/helpers/any_ref.dart';
+import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
+import 'package:observatory/src/elements/helpers/tag.dart';
+import 'package:observatory/src/elements/helpers/uris.dart';
+import 'package:observatory/src/elements/nav/bar.dart';
+import 'package:observatory/src/elements/nav/isolate_menu.dart';
+import 'package:observatory/src/elements/nav/menu.dart';
+import 'package:observatory/src/elements/nav/notify.dart';
+import 'package:observatory/src/elements/nav/refresh.dart';
+import 'package:observatory/src/elements/nav/top_menu.dart';
+import 'package:observatory/src/elements/nav/vm_menu.dart';
+import 'package:observatory/utils.dart';
+
+enum HeapSnapshotTreeMode {
+  dominatorTree,
+  groupByClass
+}
+
+class HeapSnapshotElement  extends HtmlElement implements Renderable {
+  static const tag = const Tag<HeapSnapshotElement>('heap-snapshot',
+                                          dependencies: const [
+                                            ClassRefElement.tag,
+                                            NavBarElement.tag,
+                                            NavTopMenuElement.tag,
+                                            NavVMMenuElement.tag,
+                                            NavIsolateMenuElement.tag,
+                                            NavMenuElement.tag,
+                                            NavRefreshElement.tag,
+                                            NavNotifyElement.tag,
+                                            VirtualTreeElement.tag,
+                                          ]);
+
+  RenderingScheduler<HeapSnapshotElement> _r;
+
+  Stream<RenderedEvent<HeapSnapshotElement>> get onRendered => _r.onRendered;
+
+  M.VM _vm;
+  M.IsolateRef _isolate;
+  M.EventRepository _events;
+  M.NotificationRepository _notifications;
+  M.HeapSnapshotRepository _snapshots;
+  M.InstanceRepository _instances;
+  M.HeapSnapshot _snapshot;
+  Stream<M.HeapSnapshotLoadingProgressEvent> _progressStream;
+  M.HeapSnapshotLoadingProgress _progress;
+  HeapSnapshotTreeMode _mode = HeapSnapshotTreeMode.dominatorTree;
+
+
+  M.IsolateRef get isolate => _isolate;
+  M.NotificationRepository get notifications => _notifications;
+  M.HeapSnapshotRepository get profiles => _snapshots;
+  M.VMRef get vm => _vm;
+
+  factory HeapSnapshotElement(M.VM vm, M.IsolateRef isolate,
+                            M.EventRepository events,
+                            M.NotificationRepository notifications,
+                            M.HeapSnapshotRepository snapshots,
+                            M.InstanceRepository instances,
+                            {RenderingQueue queue}) {
+    assert(vm != null);
+    assert(isolate != null);
+    assert(events != null);
+    assert(notifications != null);
+    assert(snapshots != null);
+    assert(instances != null);
+    HeapSnapshotElement e = document.createElement(tag.name);
+    e._r = new RenderingScheduler(e, queue: queue);
+    e._vm = vm;
+    e._isolate = isolate;
+    e._events = events;
+    e._notifications = notifications;
+    e._snapshots = snapshots;
+    e._instances = instances;
+    return e;
+  }
+
+  HeapSnapshotElement.created() : super.created();
+
+  @override
+  attached() {
+    super.attached();
+    _r.enable();
+    _refresh();
+  }
+
+  @override
+  detached() {
+    super.detached();
+    _r.disable(notify: true);
+    children = [];
+  }
+
+  void render() {
+    var content = [
+      new NavBarElement(queue: _r.queue)
+        ..children = [
+          new NavTopMenuElement(queue: _r.queue),
+          new NavVMMenuElement(_vm, _events, queue: _r.queue),
+          new NavIsolateMenuElement(_isolate, _events, queue: _r.queue),
+          new NavMenuElement('heap snapshot', link: Uris.profiler(_isolate),
+              last: true, queue: _r.queue),
+          new NavRefreshElement(queue: _r.queue)
+              ..disabled = M.isHeapSnapshotProgressRunning(_progress?.status)
+              ..onRefresh.listen((e) {
+                _refresh();
+              }),
+          new NavNotifyElement(_notifications, queue: _r.queue)
+        ],
+    ];
+    if (_progress == null) {
+      children = content;
+      return;
+    }
+    switch (_progress.status) {

[rmacnak, 2016/08/23 16:57:09]

Because computing the dominator tree can take quite a while for large heaps, I
think we should continuing reporting the phases of the computation so if a
particular heap makes especially slow progress we know what phase to look at
(finding successors, computing post order, etc).

[cbernaschina, 2016/08/23 17:28:28]

Done.

+      case M.HeapSnapshotLoadingStatus.fetching :
+        content.addAll(_createStatusMessage('Fetching profile from VM...'));

[rmacnak, 2016/08/23 16:57:09]

profile -> snapshot

[cbernaschina, 2016/08/23 17:28:28]

Done.

+        break;
+      case M.HeapSnapshotLoadingStatus.loading :
+        content.addAll(_createStatusMessage('Loading profile...',
+            progress: _progress.progress));
+        break;
+      case M.HeapSnapshotLoadingStatus.disabled :
+        content.addAll(_createDisabledMessage());
+        break;
+      case M.HeapSnapshotLoadingStatus.loaded:
+        content.addAll(_createReport());
+        break;
+    }
+    children = content;
+  }
+
+  Future _refresh() async {
+    _progress = null;
+    _progressStream = _snapshots.get(isolate);
+    _r.dirty();
+    _progressStream.listen((_) => _r.dirty());
+    _progress = (await _progressStream.first).progress;
+    _r.dirty();
+    if (M.isHeapSnapshotProgressRunning(_progress.status)) {
+      _progress = (await _progressStream.last).progress;
+      _snapshot = _progress.snapshot;
+      _r.dirty();
+    }
+  }
+
+  static List<Element> _createStatusMessage(String message,
+      {double progress: 0.0}) {
+    return [
+      new DivElement()..classes = ['content-centered-big']
+        ..children = [
+          new DivElement()..classes = ['statusBox', 'shadow', 'center']
+            ..children = [
+              new DivElement()..classes = ['statusMessage']
+                ..text = message,
+              new DivElement()..style.background = '#0489c3'
+                ..style.width = '$progress%'
+                ..style.height = '15px'
+                ..style.borderRadius = '4px'
+            ]
+        ]
+    ];
+  }
+
+  static List<Element> _createDisabledMessage() {

[rmacnak, 2016/08/23 16:57:09]

The profile flag has no effect on the heap snapshot, which is always available
when the vm service is available.

[cbernaschina, 2016/08/23 17:28:28]

Done

+    return [
+      new DivElement()..classes = ['content-centered-big']
+        ..children = [
+          new DivElement()..classes = ['statusBox' 'shadow' 'center']
+            ..children = [
+              new DivElement()
+                ..children = [
+                  new HeadingElement.h1()
+                  ..text = 'Profiling is disabled',
+                  new BRElement(),
+                  new DivElement()
+                    ..innerHtml = 'Perhaps the <b>profile</b> '
+                                  'flag has been disabled for this VM.',
+                  new BRElement(),
+                  new SpanElement()..text = 'See all',
+                  new AnchorElement(href: Uris.flags())..text = 'vm flags'
+                ]
+            ]
+        ]
+    ];
+  }
+
+  VirtualTreeElement _tree;
+
+  List<Element> _createReport() {
+    var report = [
+      new DivElement()..classes = ['content-centered-big']
+        ..children = [
+          new DivElement()..classes = ['memberList']
+            ..children = [
+              new DivElement()..classes = ['memberItem']
+                ..children = [
+                  new DivElement()..classes = ['memberName']
+                    ..text = 'Refreshed ',
+                  new DivElement()..classes = ['memberName']
+                    ..text = Utils.formatDateTime(_snapshot.timestamp)
+                ],
+              new DivElement()..classes = ['memberItem']
+                ..children = [
+                  new DivElement()..classes = ['memberName']
+                    ..text = 'Objects ',
+                  new DivElement()..classes = ['memberName']
+                    ..text = '${_snapshot.objects}'
+                ],
+              new DivElement()..classes = ['memberItem']
+                ..children = [
+                  new DivElement()..classes = ['memberName']
+                    ..text = 'References ',
+                  new DivElement()..classes = ['memberName']
+                    ..text = '${_snapshot.references}'
+                ],
+              new DivElement()..classes = ['memberItem']
+                ..children = [
+                  new DivElement()..classes = ['memberName']
+                    ..text = 'Size ',
+                  new DivElement()..classes = ['memberName']
+                    ..text = Utils.formatSize(_snapshot.size)
+                ],
+              new DivElement()..classes = ['memberItem']
+                ..children = [
+                  new DivElement()..classes = ['memberName']
+                    ..text = 'Analysis ',
+                  new DivElement()..classes = ['memberName']
+                    ..children = _createModeSelect()
+                ]
+            ]
+        ],
+    ];
+    switch (_mode) {
+      case HeapSnapshotTreeMode.dominatorTree:
+        _tree = new VirtualTreeElement(_createDominator, _updateDominator,
+            _getChildrenDominator,
+            items: _getChildrenDominator(_snapshot.dominatorTree),
+            queue: _r.queue);
+        _tree.expand(_snapshot.dominatorTree);
+        final text = 'In a heap dominator tree, an object X is a parent of '
+                     'object Y if every path from the root to Y goes through '
+                     'X. This allows you to find "choke points" that are '
+                     'holding onto a lot memory. If an object becomes garbage, '

[rmacnak, 2016/08/23 16:57:09]

a lot of memory

[cbernaschina, 2016/08/23 17:28:28]

Done.

+                     'all its children in the dominator tree become garbage as '
+                     'well. The retained size of an object is the sum of the '
+                     'retained sizes of its children in the dominator tree '
+                     'plus its own shallow size, and is the amount of memory '
+                     'that would be freed if the object became garbage.';
+        report.addAll([
+          new DivElement()..classes = ['content-centered-big', 'explanation']
+            ..text = text
+            ..title = text,
+          _tree
+        ]);
+        break;
+      case HeapSnapshotTreeMode.groupByClass:
+        final items = _snapshot.classReferences.toList();
+        items.sort((a, b) => b.shallowSize - a.shallowSize);
+        _tree = new VirtualTreeElement(_createGroup, _updateGroup,
+            _getChildrenGroup, items: items, queue: _r.queue);
+        _tree.expand(_snapshot.dominatorTree);
+        report.add(_tree);
+        break;
+      default:
+        break;
+    }
+    return report;
+  }
+
+  static Element _createDominator(toggle) {
+    return new DivElement()
+      ..classes = const ['tree-item']
+      ..children = [
+        new SpanElement()..classes = const ['size']
+          ..title = 'retained size',
+        new SpanElement()..classes = const ['lines'],
+        new ButtonElement()..classes = const ['expander']
+          ..onClick.listen((_) => toggle(autoToggleSingleChildNodes: true)),
+        new SpanElement()..classes = const ['percentage']
+          ..title = 'percentage of heap being retained',
+        new SpanElement()..classes = const ['name']
+      ];
+  }
+
+  static Element _createGroup(toggle) {
+    return new DivElement()
+      ..classes = const ['tree-item']
+      ..children = [
+        new SpanElement()..classes = const ['size']
+          ..title = 'shallow size',
+        new SpanElement()..classes = const ['lines'],
+        new ButtonElement()..classes = const ['expander']
+          ..onClick.listen((_) => toggle(autoToggleSingleChildNodes: true)),
+        new SpanElement()..classes = const ['count']
+          ..title = 'shallow size',
+        new SpanElement()..classes = const ['name']
+      ];
   }
 
   static const int kMaxChildren = 100;
   static const int kMinRetainedSize = 4096;
 
-  void onShow() {
-    super.onShow();
-    if (children.length == 0) {
-      domTreeChildren.sort((a, b) => b.retainedSize - a.retainedSize);
-      int includedChildren = 0;
-      for (var childVertex in domTreeChildren) {
-        if (childVertex.retainedSize >= kMinRetainedSize) {
-          if (++includedChildren <= kMaxChildren) {
-            var row = new DominatorTreeRow(tree, this, childVertex, snapshot);
-            children.add(row);
-          }
-        }
+  static _getChildrenDominator(M.HeapSnapshotDominatorNode node) {
+    final list = node.children.toList();
+    list.sort((a, b) => b.retainedSize - a.retainedSize);
+    return list.where((child) => child.retainedSize >= kMinRetainedSize)
+               .take(kMaxChildren);
+  }
+
+  static _getChildrenGroup(item) {
+    if (item is M.HeapSnapshotClassReferences) {
+      if (item.inbounds.isNotEmpty || item.outbounds.isNotEmpty) {
+        return [item.inbounds, item.outbounds];
       }
-    }
-
-    var firstColumn = flexColumns[0];
-    firstColumn.style.justifyContent = 'flex-start';
-    firstColumn.style.position = 'relative';
-    firstColumn.style.alignItems = 'center';
-    firstColumn.style.setProperty('overflow-x', 'hidden');
-
-    var percentRetained = vertex.retainedSize / snapshot.graph.size;
-    var percentNode = new SpanElement();
-    percentNode.text =  Utils.formatPercentNormalized(percentRetained);
-    percentNode.style.minWidth = '5em';
-    percentNode.style.textAlign = 'right';
-    percentNode.title = "Percent of heap being retained";
-    percentNode.style.display = 'inline-block';
-    firstColumn.children.add(percentNode);
-
-    var gap = new SpanElement();
-    gap.style.minWidth = '1em';
-    gap.style.display = 'inline-block';
-    firstColumn.children.add(gap);
-
-    AnyServiceRefElement objectRef = new Element.tag("any-service-ref");
-    snapshot.isolate.getObjectByAddress(vertex.address).then((obj) {
-      objectRef.ref = obj;
+    } else if (item is Iterable) {
+      return item.toList()..sort((a, b) => b.shallowSize - a.shallowSize);
+    }
+    return const [];
+  }
+
+  void _updateDominator(HtmlElement element, M.HeapSnapshotDominatorNode node,
+      int depth) {
+    element.children[0].text = Utils.formatSize(node.shallowSize);

[rmacnak, 2016/08/23 17:01:02]

retainedSize

[cbernaschina, 2016/08/23 17:28:28]

Done.

+    _updateLines(element.children[1].children, depth);
+    if (_getChildrenDominator(node).isNotEmpty) {
+      element.children[2].text = _tree.isExpanded(node) ? '▼' : '►';
+    } else {
+      element.children[2].text = '';
+    }
+    element.children[3].text = Utils.formatPercentNormalized(
+        node.retainedSize * 1.0 / _snapshot.size);
+    final wrapper = new SpanElement()..classes = const ['name']
+                                     ..text = 'Loading...';
+    element.children[4] = wrapper;
+    node.object.then((object) {
+      wrapper..text = ''
+        ..children = [anyRef(_isolate, object, _instances, queue: _r.queue)];
     });
-    objectRef.style.alignSelf = 'center';
-    firstColumn.children.add(objectRef);
-
-    var secondColumn = flexColumns[1];
-    secondColumn.style.justifyContent = 'flex-end';
-    secondColumn.style.position = 'relative';
-    secondColumn.style.alignItems = 'center';
-    secondColumn.style.paddingRight = '0.5em';
-    secondColumn.text = Utils.formatSize(vertex.retainedSize);
+  }
+
+  void _updateGroup(HtmlElement element, item, int depth) {
+    _updateLines(element.children[1].children, depth);
+    if (item is M.HeapSnapshotClassReferences) {
+      element.children[0].text = Utils.formatSize(item.shallowSize);
+      element.children[2].text = _tree.isExpanded(item) ? '▼' : '►';
+      element.children[3].text = '${item.instances} instances of ';
+      element.children[4] = new ClassRefElement(_isolate, item.clazz,
+          queue: _r.queue)..classes = const ['name'];
+    } else if (item is Iterable) {
+      element.children[0].text = '';
+      if (item.isNotEmpty) {
+        element.children[2].text = _tree.isExpanded(item) ? '▼' : '►';
+      } else {
+        element.children[2].text = '';
+      }
+      element.children[3].text = '';
+      if (item is Iterable<M.HeapSnapshotClassInbound>) {
+        element.children[4] = new SpanElement()..classes = const ['name']
+            ..text = '${item.length} Ingoing references';
+      } else {
+        element.children[4] = new SpanElement()..classes = const ['name']
+            ..text = '${item.length} Outgoing references';
+      }
+    } else {
+      element.children[0].text = '';
+      element.children[2].text = '';
+      element.children[3].text = '';
+      element.children[4] = new SpanElement()..classes = const ['name'];
+      if (item is M.HeapSnapshotClassInbound){
+        element.children[3].text =
+            '${item.count} references from instances of ';
+        element.children[4].children = [
+          new ClassRefElement(_isolate, item.source,
+            queue: _r.queue)
+        ];
+      } else if (item is M.HeapSnapshotClassOutbound){
+        element.children[3]..text = '${item.count} references to instances of ';
+        element.children[4].children = [
+          new ClassRefElement(_isolate, item.target,
+            queue: _r.queue)
+        ];
+      }
+    }
+  }
+
+  static _updateLines(List<Element> lines, int n) {
+    n = Math.max(0, n);
+    while (lines.length > n) {
+      lines.removeLast();
+    }
+    while (lines.length < n) {
+      lines.add(new SpanElement());
+    }
+  }
+
+  static String modeToString(HeapSnapshotTreeMode mode) {
+    switch (mode) {
+      case HeapSnapshotTreeMode.dominatorTree: return 'Dominator tree';
+      case HeapSnapshotTreeMode.groupByClass: return 'Group by class';
+    }
+    throw new Exception('Unknown ProfileTreeMode');
+  }
+
+  List<Element> _createModeSelect() {
+    var s;
+    return [
+      s = new SelectElement()..classes = ['analysis-select']
+        ..value = modeToString(_mode)
+        ..children = HeapSnapshotTreeMode.values.map((mode) {
+            return new OptionElement(value: modeToString(mode),
+                selected: _mode == mode)
+              ..text = modeToString(mode);
+          }).toList(growable: false)
+        ..onChange.listen((_) {
+            _mode = HeapSnapshotTreeMode.values[s.selectedIndex];
+            _r.dirty();
+          })
+    ];
   }
 }
-
-
-class MergedVerticesRow extends TableTreeRow {
-  final Isolate isolate;
-  final List<MergedVertex> mergedVertices;
-
-  MergedVerticesRow(TableTree tree,
-                   TableTreeRow parent,
-                   this.isolate,
-                   this.mergedVertices)
-      : super(tree, parent) {
-  }
-
-  bool hasChildren() {
-    return mergedVertices.length > 0;
-  }
-
-  void onShow() {
-    super.onShow();
-
-    if (children.length == 0) {
-      mergedVertices.sort((a, b) => b.shallowSize - a.shallowSize);
-      for (var mergedVertex in mergedVertices) {
-        if (mergedVertex.instances > 0) {
-          var row = new MergedVertexRow(tree, this, isolate, mergedVertex);
-          children.add(row);
-        }
-      }
-    }
-  }
-}
-
-class MergedVertexRow extends TableTreeRow {
-  final Isolate isolate;
-  final MergedVertex vertex;
-
-  MergedVertexRow(TableTree tree,
-                  TableTreeRow parent,
-                  this.isolate,
-                  this.vertex)
-      : super(tree, parent) {
-  }
-
-  bool hasChildren() {
-    return vertex.outgoingEdges.length > 0 ||
-           vertex.incomingEdges.length > 0;
-  }
-
-  void onShow() {
-    super.onShow();
-    if (children.length == 0) {
-      children.add(new MergedEdgesRow(tree, this, isolate, vertex, true));
-      children.add(new MergedEdgesRow(tree, this, isolate, vertex, false));
-    }
-
-
-    var firstColumn = flexColumns[0];
-    firstColumn.style.justifyContent = 'flex-start';
-    firstColumn.style.position = 'relative';
-    firstColumn.style.alignItems = 'center';
-
-    var percentNode = new SpanElement();
-    percentNode.text = "${vertex.instances} instances of";
-    percentNode.style.minWidth = '5em';
-    percentNode.style.textAlign = 'right';
-    firstColumn.children.add(percentNode);
-
-    var gap = new SpanElement();
-    gap.style.minWidth = '1em';
-    gap.style.display = 'inline-block';
-    firstColumn.children.add(gap);
-
-    ClassRefElementWrapper classRef = new Element.tag("class-ref");
-    classRef.ref = isolate.getClassByCid(vertex.cid);
-    classRef.style.alignSelf = 'center';
-    firstColumn.children.add(classRef);
-
-    var secondColumn = flexColumns[1];
-    secondColumn.style.justifyContent = 'flex-end';
-    secondColumn.style.position = 'relative';
-    secondColumn.style.alignItems = 'center';
-    secondColumn.style.paddingRight = '0.5em';
-    secondColumn.text = Utils.formatSize(vertex.shallowSize);
-  }
-}
-
-class MergedEdgesRow extends TableTreeRow {
-  final Isolate isolate;
-  final MergedVertex vertex;
-  final bool outgoing;
-
-  MergedEdgesRow(TableTree tree,
-                 TableTreeRow parent,
-                 this.isolate,
-                 this.vertex,
-                 this.outgoing)
-      : super(tree, parent) {
-  }
-
-  bool hasChildren() {
-    return outgoing
-            ? vertex.outgoingEdges.length > 0
-            : vertex.incomingEdges.length > 0;
-  }
-
-  void onShow() {
-    super.onShow();
-    if (children.length == 0) {
-      if (outgoing) {
-        var outgoingEdges = vertex.outgoingEdges.values.toList();
-        outgoingEdges.sort((a, b) => b.shallowSize - a.shallowSize);
-        for (var edge in outgoingEdges) {
-          if (edge.count > 0) {
-            var row = new MergedEdgeRow(tree, this, isolate, edge, true);
-            children.add(row);
-          }
-        }
-      } else {
-        vertex.incomingEdges.sort((a, b) => b.shallowSize - a.shallowSize);
-        for (var edge in vertex.incomingEdges) {
-          if (edge.count > 0) {
-            var row = new MergedEdgeRow(tree, this, isolate, edge, false);
-            children.add(row);
-          }
-        }
-      }
-    }
-
-    var count = 0;
-    var shallowSize = 0;
-    var edges = outgoing ? vertex.outgoingEdges.values : vertex.incomingEdges;
-    for (var edge in edges) {
-      count += edge.count;
-      shallowSize += edge.shallowSize;
-    }
-
-    var firstColumn = flexColumns[0];
-    firstColumn.style.justifyContent = 'flex-start';
-    firstColumn.style.position = 'relative';
-    firstColumn.style.alignItems = 'center';
-
-    var countNode = new SpanElement();
-    countNode.text = "$count";
-    countNode.style.minWidth = '5em';
-    countNode.style.textAlign = 'right';
-    firstColumn.children.add(countNode);
-
-    var gap = new SpanElement();
-    gap.style.minWidth = '1em';
-    gap.style.display = 'inline-block';
-    firstColumn.children.add(gap);
-
-    var labelNode = new SpanElement();
-    labelNode.text = outgoing ? "Outgoing references" : "Incoming references";
-    firstColumn.children.add(labelNode);
-
-    var secondColumn = flexColumns[1];
-    secondColumn.style.justifyContent = 'flex-end';
-    secondColumn.style.position = 'relative';
-    secondColumn.style.alignItems = 'center';
-    secondColumn.style.paddingRight = '0.5em';
-    secondColumn.text = Utils.formatSize(shallowSize);
-  }
-}
-
-class MergedEdgeRow extends TableTreeRow {
-  final Isolate isolate;
-  final MergedEdge edge;
-  final bool outgoing;
-
-  MergedEdgeRow(TableTree tree,
-                TableTreeRow parent,
-                this.isolate,
-                this.edge,
-                this.outgoing)
-      : super(tree, parent) {
-  }
-
-  bool hasChildren() => false;
-
-  void onShow() {
-    super.onShow();
-
-    var firstColumn = flexColumns[0];
-    firstColumn.style.justifyContent = 'flex-start';
-    firstColumn.style.position = 'relative';
-    firstColumn.style.alignItems = 'center';
-
-    var percentNode = new SpanElement();
-    var preposition = outgoing ? "to" : "from";
-    percentNode.text = "${edge.count} references $preposition instances of";
-    percentNode.style.minWidth = '5em';
-    percentNode.style.textAlign = 'right';
-    firstColumn.children.add(percentNode);
-
-    var gap = new SpanElement();
-    gap.style.minWidth = '1em';
-    gap.style.display = 'inline-block';
-    firstColumn.children.add(gap);
-
-    MergedVertex v = outgoing ? edge.target : edge.source;
-    if (v.cid == 0) {
-      var rootName = new SpanElement();
-      rootName.text = '<root>';
-      firstColumn.children.add(rootName);
-    } else {
-      ClassRefElementWrapper classRef = new Element.tag("class-ref");
-      classRef.ref = isolate.getClassByCid(v.cid);
-      classRef.style.alignSelf = 'center';
-      firstColumn.children.add(classRef);
-    }
-
-    var secondColumn = flexColumns[1];
-    secondColumn.style.justifyContent = 'flex-end';
-    secondColumn.style.position = 'relative';
-    secondColumn.style.alignItems = 'center';
-    secondColumn.style.paddingRight = '0.5em';
-    secondColumn.text = Utils.formatSize(edge.shallowSize);
-  }
-}
-
-
-class MergedEdge {
-  final MergedVertex source;
-  final MergedVertex target;
-  int count = 0;
-  int shallowSize = 0;
-  int retainedSize = 0;
-
-  MergedEdge(this.source, this.target);
-}
-
-class MergedVertex {
-  final int cid;
-  int instances = 0;
-  int shallowSize = 0;
-  int retainedSize = 0;
-
-  List<MergedEdge> incomingEdges = new List<MergedEdge>();
-  Map<int, MergedEdge> outgoingEdges = new Map<int, MergedEdge>();
-
-  MergedVertex(this.cid);
-}
-
-
-Future<List<MergedVertex>> buildMergedVertices(ObjectGraph graph) async {
-  Logger.root.info("Start merge vertices");
-
-  var cidToMergedVertex = {};
-
-  for (var vertex in graph.vertices) {
-    var cid = vertex.vmCid;
-    MergedVertex source = cidToMergedVertex[cid];
-    if (source == null) {
-      cidToMergedVertex[cid] = source = new MergedVertex(cid);
-    }
-
-    source.instances++;
-    source.shallowSize += (vertex.shallowSize == null ? 0 : vertex.shallowSize);
-
-    for (var vertex2 in vertex.successors) {
-      var cid2 = vertex2.vmCid;
-      MergedEdge edge = source.outgoingEdges[cid2];
-      if (edge == null) {
-        MergedVertex target = cidToMergedVertex[cid2];
-        if (target == null) {
-          cidToMergedVertex[cid2] = target = new MergedVertex(cid2);
-        }
-        edge = new MergedEdge(source, target);
-        source.outgoingEdges[cid2] = edge;
-        target.incomingEdges.add(edge);
-      }
-      edge.count++;
-      // An over-estimate if there are multiple references to the same object.
-      edge.shallowSize += vertex2.shallowSize == null ? 0 : vertex2.shallowSize;
-    }
-  }
-
-  Logger.root.info("End merge vertices");
-
-  return cidToMergedVertex.values.toList();
-}
-
-@CustomTag('heap-snapshot')
-class HeapSnapshotElement extends ObservatoryElement {
-  @published Isolate isolate;
-  @observable HeapSnapshot snapshot;
-
-  @published String state = 'Requested';
-  @published String analysisSelector = 'DominatorTree';
-
-  HeapSnapshotElement.created() : super.created();
-
-  void analysisSelectorChanged(oldValue) {
-    _update();
-  }
-
-  void isolateChanged(oldValue) {
-    if (isolate == null) return;
-
-    if (isolate.latestSnapshot == null) {
-      _getHeapSnapshot();
-    } else {
-      snapshot = isolate.latestSnapshot;
-      state = 'Loaded';
-      _update();
-    }
-  }
-
-  Future refresh() {
-    return _getHeapSnapshot();
-  }
-
-  Future _getHeapSnapshot() {
-    var completer = new Completer();
-    state = "Requesting heap snapshot...";
-    isolate.getClassRefs();
-
-    bool collectGarbage =
-        app.locationManager.getBoolParameter('collectGarbage', true);
-
-    var stopwatch = new Stopwatch()..start();
-    isolate.fetchHeapSnapshot(collectGarbage).listen((event) {
-      if (event is String) {
-        print("${stopwatch.elapsedMilliseconds} $event");
-        state = event;
-      } else if (event is HeapSnapshot) {
-        snapshot = event;
-        state = 'Loaded';
-        completer.complete(snapshot);
-        _update();
-      } else {
-        throw "Unexpected event $event";
-      }
-    });
-    return completer.future;
-  }
-
-  void _update() {
-    if (snapshot == null) {
-      return;
-    }
-
-    switch(analysisSelector) {
-    case 'DominatorTree':
-      _buildDominatorTree();
-      break;
-    case 'MergeByClass':
-      _buildMergedVertices();
-      break;
-    }
-  }
-
-  void _buildDominatorTree() {
-    var tableBody = shadowRoot.querySelector('#treeBody');
-    var tree = new TableTree(tableBody, 2);
-    var rootRow =
-        new DominatorTreeRow(tree, null, snapshot.graph.root, snapshot);
-    tree.initialize(rootRow);
-    return;
-  }
-
-  void _buildMergedVertices() {
-    state = 'Grouping...';
-    var tableBody = shadowRoot.querySelector('#treeBody');
-    var tree = new TableTree(tableBody, 2);
-    tableBody.children.clear();
-
-    new Future.delayed(const Duration(milliseconds: 500), () {
-      buildMergedVertices(snapshot.graph).then((vertices) {
-        state = 'Loaded';
-        var rootRow = new MergedVerticesRow(tree, null, isolate, vertices);
-        tree.initialize(rootRow);
-      });
-    });
-  }
-}