Support for modular mixin resolution.

pkg/kernel/lib/binary/ast_to_binary.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 library kernel.ast_to_binary;
 
 import '../ast.dart';
 import '../import_table.dart';
 import 'tag.dart';
 import 'dart:convert';
 import 'dart:typed_data';
@@ skipping 265 matching lines @@
 
   void writeAnnotation(Expression annotation) {
     _variableIndexer ??= new VariableIndexer();
     writeNode(annotation);
   }
 
   void writeAnnotationList(List<Expression> annotations) {
     writeList(annotations, writeAnnotation);
   }
 
+  int _encodeClassFlags(bool isAbstract, ClassLevel level) {
+    int abstactFlag = isAbstract ? 1 : 0;
+    int levelFlags = (level.index - 1) << 1;
+    return abstactFlag | levelFlags;
+  }
+
   visitClass(Class node) {
-    int flags = node.isAbstract ? 1 : 0;
-    if (node.level == ClassLevel.Type) {
-      flags |= 0x2;
-    }
+    int flags = _encodeClassFlags(node.isAbstract, node.level);
     if (node.isMixinApplication) {
       writeByte(Tag.MixinClass);
       writeOffset(node, node.fileOffset);
       writeByte(flags);
       writeStringReference(node.name ?? '');
       writeUriReference(node.fileUri ?? '');
       writeAnnotationList(node.annotations);
       _typeParameterIndexer.enter(node.typeParameters);
       writeNodeList(node.typeParameters);
       writeNode(node.supertype);
@@ skipping 940 matching lines @@
   void flush() {
     _sink.add(_buffer.sublist(0, length));
     _buffer = new Uint8List(SIZE);
     length = 0;
   }
 
   void flushAndDestroy() {
     _sink.add(_buffer.sublist(0, length));
   }
 }