Address static warnings in the service library and tests.

runtime/bin/vmservice/observatory/lib/src/service/object.dart

Index: runtime/bin/vmservice/observatory/lib/src/service/object.dart
diff --git a/runtime/bin/vmservice/observatory/lib/src/service/object.dart b/runtime/bin/vmservice/observatory/lib/src/service/object.dart
index 67747026f2b044182249cb75318f07d7bfb38b8d..2b35a99eedebd11dd9691dea8019d1ebb2f88a88 100644
--- a/runtime/bin/vmservice/observatory/lib/src/service/object.dart
+++ b/runtime/bin/vmservice/observatory/lib/src/service/object.dart
@@ -1528,12 +1528,10 @@ class Context extends ServiceObject {
   @observable Class clazz;
   @observable int size;
 
-  @observable ServiceObject parentContext;
-  @observable var length;
+  @observable var parentContext;
+  @observable int length;
   @observable var variables;
 
-  bool get isClosure => closureFunc != null;
-
   Context._empty(ServiceObjectOwner owner) : super._empty(owner);
 
   void _update(ObservableMap map, bool mapIsRef) {
@@ -1555,8 +1553,6 @@ class Context extends ServiceObject {
     _loaded = true;
   }
 
-  String get shortName => valueAsString != null ? valueAsString : 'a ${clazz.name}';
-
   String toString() => 'Context($length)';
 }