Omnibus Observatory UI fixes:

runtime/observatory/tests/observatory_ui/heap_snapshot/element_test.dart

Index: runtime/observatory/tests/observatory_ui/heap_snapshot/element_test.dart
diff --git a/runtime/observatory/tests/observatory_ui/heap_snapshot/element_test.dart b/runtime/observatory/tests/observatory_ui/heap_snapshot/element_test.dart
index 6e7b6160be86ecb7e896531ba7928c6781f6c3a5..ecebb93c4e3d016f069a3cc9743d9ee0223d066f 100644
--- a/runtime/observatory/tests/observatory_ui/heap_snapshot/element_test.dart
+++ b/runtime/observatory/tests/observatory_ui/heap_snapshot/element_test.dart
@@ -20,10 +20,10 @@ main() {
   final events = new EventRepositoryMock();
   final notifs = new NotificationRepositoryMock();
   final snapshots = new HeapSnapshotRepositoryMock();
-  final instances = new InstanceRepositoryMock();
+  final objects = new ObjectRepositoryMock();
   test('instantiation', () {
     final e = new HeapSnapshotElement(
-        vm, isolate, events, notifs, snapshots, instances);
+        vm, isolate, events, notifs, snapshots, objects);
     expect(e, isNotNull, reason: 'element correctly created');
   });
   test('elements created', () async {
@@ -36,7 +36,7 @@ main() {
       return controller.stream;
     });
     final e = new HeapSnapshotElement(
-        vm, isolate, events, notifs, snapshots, instances);
+        vm, isolate, events, notifs, snapshots, objects);
     document.body.append(e);
     await e.onRendered.first;
     expect(e.children.length, isNonZero, reason: 'has elements');