Use ClassHierarchy.applyChanges() in MixinFullResolution.

pkg/kernel/lib/src/incremental_class_hierarchy.dart

Index: pkg/kernel/lib/src/incremental_class_hierarchy.dart
diff --git a/pkg/kernel/lib/src/incremental_class_hierarchy.dart b/pkg/kernel/lib/src/incremental_class_hierarchy.dart
index eaa0f2dc724a8825c1f2061be45b95db3545a729..f8241b7e2ccafb10c7b895811eec597186a15520 100644
--- a/pkg/kernel/lib/src/incremental_class_hierarchy.dart
+++ b/pkg/kernel/lib/src/incremental_class_hierarchy.dart
@@ -79,6 +79,12 @@ class IncrementalClassHierarchy implements ClassHierarchy {
   final Map<Class, _ClassInfo> _info = new LinkedHashMap<Class, _ClassInfo>();
 
   @override
+  ClassHierarchy applyChanges(Iterable<Class> changed) {
+    if (changed.isEmpty) return this;
+    return new IncrementalClassHierarchy();
+  }
+
+  @override
   void forEachOverridePair(Class node,
       callback(Member declaredMember, Member interfaceMember, bool isSetter)) {
     _ClassInfo info = _getInfo(node);