Expose getInterfaceMembers method through ClassHierarchy.

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 051aae18f61db5692b6ed52f17ae05f4cff69569..b99956ee2a473d33c7955e4b90bb4e2dd2b96650 100644
--- a/pkg/kernel/lib/src/incremental_class_hierarchy.dart
+++ b/pkg/kernel/lib/src/incremental_class_hierarchy.dart
@@ -270,6 +270,12 @@ class IncrementalClassHierarchy implements ClassHierarchy {
     return _findMemberByName(members, name);
   }
 
+  @override
+  List<Member> getInterfaceMembers(Class class_, {bool setters: false}) {
+    var info = _getInfo(class_);
+    return setters ? info.interfaceSetters : info.interfaceGettersAndCalls;
+  }
+
   @override
   Iterable<Class> getOrderedClasses(Iterable<Class> unordered) {
     unordered.forEach(_getInfo);