Omnibus Observatory UI fixes:

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

Index: runtime/observatory/tests/observatory_ui/context_ref/element_test.dart
diff --git a/runtime/observatory/tests/observatory_ui/context_ref/element_test.dart b/runtime/observatory/tests/observatory_ui/context_ref/element_test.dart
index 3ab0a667a0e76f3c507216f3901c0662a5ed0e17..dadeb4d3f45d5adc18aa560e937c2c6d3c0c40f0 100644
--- a/runtime/observatory/tests/observatory_ui/context_ref/element_test.dart
+++ b/runtime/observatory/tests/observatory_ui/context_ref/element_test.dart
@@ -12,14 +12,16 @@ main() {
 
   const isolate = const IsolateRefMock();
   const context = const ContextRefMock();
+  final objects = new ObjectRepositoryMock();
+
   test('instantiation', () {
-    final e = new ContextRefElement(isolate, context);
+    final e = new ContextRefElement(isolate, context, objects);
     expect(e, isNotNull, reason: 'element correctly created');
     expect(e.isolate, equals(isolate));
     expect(e.context, equals(context));
   });
   test('elements created after attachment', () async {
-    final e = new ContextRefElement(isolate, context);
+    final e = new ContextRefElement(isolate, context, objects);
     document.body.append(e);
     await e.onRendered.first;
     expect(e.children.length, isNonZero, reason: 'has elements');