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

runtime/observatory/tests/service/object_graph_vm_test.dart

Index: runtime/observatory/tests/service/object_graph_vm_test.dart
diff --git a/runtime/observatory/tests/service/graph_test.dart b/runtime/observatory/tests/service/object_graph_vm_test.dart
similarity index 95%
rename from runtime/observatory/tests/service/graph_test.dart
rename to runtime/observatory/tests/service/object_graph_vm_test.dart
index 85556baf97f4ea6e2dd2c3ad5464248cf49d66fc..eae16795a9de842ded7bc1ba8a71568d999e864f 100644
--- a/runtime/observatory/tests/service/graph_test.dart
+++ b/runtime/observatory/tests/service/object_graph_vm_test.dart
@@ -4,6 +4,7 @@
 // VMOptions=--error_on_bad_type --error_on_bad_override
 
 import 'package:observatory/heap_snapshot.dart';
+import 'package:observatory/models.dart' as M;
 import 'package:observatory/object_graph.dart';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
@@ -43,7 +44,8 @@ var tests = [
   Class fooClass = lib.classes.first;
   fooId = fooClass.vmCid;
 
-  RawHeapSnapshot raw = await isolate.fetchHeapSnapshot(false).last;
+  RawHeapSnapshot raw =
+      await isolate.fetchHeapSnapshot(M.HeapSnapshotRoots.vm, false).last;
   HeapSnapshot snapshot = new HeapSnapshot();
   await snapshot.loadProgress(isolate, raw).last;
   ObjectGraph graph = snapshot.graph;