Omnibus Observatory UI fixes:

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

Index: runtime/observatory/tests/observatory_ui/megamorphiccache_view/element_test.dart
diff --git a/runtime/observatory/tests/observatory_ui/megamorphiccache_view/element_test.dart b/runtime/observatory/tests/observatory_ui/megamorphiccache_view/element_test.dart
index f7783ba706e48dd8035332030d2a442654e8de4c..7024d417379858c71a49bb7b65b6beba921673e7 100644
--- a/runtime/observatory/tests/observatory_ui/megamorphiccache_view/element_test.dart
+++ b/runtime/observatory/tests/observatory_ui/megamorphiccache_view/element_test.dart
@@ -25,7 +25,7 @@ main() {
   final retainedSizes = new RetainedSizeRepositoryMock();
   final inbounds = new InboundReferencesRepositoryMock();
   final paths = new RetainingPathRepositoryMock();
-  final instances = new InstanceRepositoryMock();
+  final objects = new ObjectRepositoryMock();
   test('instantiation', () {
     final e = new MegamorphicCacheViewElement(
         vm,
@@ -38,7 +38,7 @@ main() {
         reachableSizes,
         inbounds,
         paths,
-        instances);
+        objects);
     expect(e, isNotNull, reason: 'element correctly created');
     expect(e.isolate, equals(isolate));
     expect(e.cache, equals(cache));
@@ -61,7 +61,7 @@ main() {
         reachableSizes,
         inbounds,
         paths,
-        instances);
+        objects);
     document.body.append(e);
     await e.onRendered.first;
     expect(e.children.length, isNonZero, reason: 'has elements');