Add a version of heap snapshots that use only fields and stack frames as roots and only include ins…

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

Index: runtime/observatory/lib/src/elements/heap_snapshot.dart
diff --git a/runtime/observatory/lib/src/elements/heap_snapshot.dart b/runtime/observatory/lib/src/elements/heap_snapshot.dart
index 7389daa2aaea72ea8b4da9e9362cce68612f9534..830e1a0b7229551cb0b4827237d7011df01a20d3 100644
--- a/runtime/observatory/lib/src/elements/heap_snapshot.dart
+++ b/runtime/observatory/lib/src/elements/heap_snapshot.dart
@@ -17,6 +17,7 @@ import 'package:observatory/src/elements/helpers/nav_bar.dart';
 import 'package:observatory/src/elements/helpers/nav_menu.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/isolate_menu.dart';
 import 'package:observatory/src/elements/nav/notify.dart';
 import 'package:observatory/src/elements/nav/refresh.dart';
@@ -51,6 +52,7 @@ class HeapSnapshotElement extends HtmlElement implements Renderable {
   M.HeapSnapshot _snapshot;
   Stream<M.HeapSnapshotLoadingProgressEvent> _progressStream;
   M.HeapSnapshotLoadingProgress _progress;
+  M.HeapSnapshotRoots _roots = M.HeapSnapshotRoots.user;
   HeapSnapshotTreeMode _mode = HeapSnapshotTreeMode.dominatorTree;
 
   M.IsolateRef get isolate => _isolate;
@@ -138,7 +140,9 @@ class HeapSnapshotElement extends HtmlElement implements Renderable {
 
   Future _refresh() async {
     _progress = null;
-    _progressStream = _snapshots.get(isolate);
+    _progressStream = _snapshots.get(isolate,
+                                     roots: _roots,
+                                     gc: true);
     _r.dirty();
     _progressStream.listen((e) {
       _progress = e.progress;
@@ -233,6 +237,16 @@ class HeapSnapshotElement extends HtmlElement implements Renderable {
                 ..children = [
                   new DivElement()
                     ..classes = ['memberName']
+                    ..text = 'Roots ',
+                  new DivElement()
+                    ..classes = ['memberName']
+                    ..children = _createRootsSelect()
+                ],
+              new DivElement()
+                ..classes = ['memberItem']
+                ..children = [
+                  new DivElement()
+                    ..classes = ['memberName']
                     ..text = 'Analysis ',
                   new DivElement()
                     ..classes = ['memberName']
@@ -396,11 +410,20 @@ class HeapSnapshotElement extends HtmlElement implements Renderable {
       ..classes = ['name']
       ..text = 'Loading...';
     element.children[4] = wrapper;
-    node.object.then((object) {
+    if (node.isStack) {
       wrapper
         ..text = ''
-        ..children = [anyRef(_isolate, object, _instances, queue: _r.queue)];
-    });
+        ..children = [
+          new AnchorElement(href: Uris.debugger(isolate))
+            ..text = 'stack frames'
+        ];
+    } else {
+      node.object.then((object) {
+        wrapper
+          ..text = ''
+          ..children = [anyRef(_isolate, object, _instances, queue: _r.queue)];
+      });
+    }
   }
 
   void _updateMergedDominator(
@@ -418,14 +441,23 @@ class HeapSnapshotElement extends HtmlElement implements Renderable {
       ..classes = ['name']
       ..text = 'Loading...';
     element.children[4] = wrapper;
-    node.klass.then((klass) {
+    if (node.isStack) {
       wrapper
         ..text = ''
         ..children = [
-          new SpanElement()..text = '${node.instanceCount} instances of ',
-          anyRef(_isolate, klass, _instances, queue: _r.queue)
+          new AnchorElement(href: Uris.debugger(isolate))
+            ..text = 'stack frames'
         ];
-    });
+    } else {
+      node.klass.then((klass) {
+        wrapper
+          ..text = ''
+          ..children = [
+            new SpanElement()..text = '${node.instanceCount} instances of ',
+            anyRef(_isolate, klass, _instances, queue: _r.queue)
+          ];
+      });
+    }
   }
 
   void _updateGroup(HtmlElement element, item, int depth) {
@@ -487,6 +519,34 @@ class HeapSnapshotElement extends HtmlElement implements Renderable {
     }
   }
 
+  static String rootsToString(M.HeapSnapshotRoots roots) {
+    switch (roots) {
+      case M.HeapSnapshotRoots.user:
+        return 'User';
+      case M.HeapSnapshotRoots.vm:
+        return 'VM';
+    }
+    throw new Exception('Unknown HeapSnapshotRoots');
+  }
+
+  List<Element> _createRootsSelect() {
+    var s;
+    return [
+      s = new SelectElement()
+        ..classes = ['roots-select']
+        ..value = rootsToString(_roots)
+        ..children = M.HeapSnapshotRoots.values.map((roots) {
+          return new OptionElement(
+              value: rootsToString(roots),
+              selected: _roots == roots)..text = rootsToString(roots);
+        }).toList(growable: false)
+        ..onChange.listen((_) {
+          _roots = M.HeapSnapshotRoots.values[s.selectedIndex];
+          _refresh();
+        })
+    ];
+  }
+
   static String modeToString(HeapSnapshotTreeMode mode) {
     switch (mode) {
       case HeapSnapshotTreeMode.dominatorTree:
@@ -496,7 +556,7 @@ class HeapSnapshotElement extends HtmlElement implements Renderable {
       case HeapSnapshotTreeMode.groupByClass:
         return 'Group by class';
     }
-    throw new Exception('Unknown ProfileTreeMode');
+    throw new Exception('Unknown HeapSnapshotTreeMode');
   }
 
   List<Element> _createModeSelect() {