Use summary IDL file for interface classes.

pkg/analyzer/lib/src/summary/summarize_const_expr.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 serialization.summarize_const_expr;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/summary/format.dart';
+import 'package:analyzer/src/summary/idl.dart';
 
 /**
  * Instances of this class keep track of intermediate state during
  * serialization of a single constant [Expression].
  */
 abstract class AbstractConstExprSerializer {
   /**
    * See [UnlinkedConstBuilder.operations].
    */
   final List<UnlinkedConstOperation> operations = <UnlinkedConstOperation>[];
@@ skipping 286 matching lines @@
  * Error that describes a problem during a constant expression serialization.
  */
 class _ConstExprSerializationError {
   final String message;
 
   _ConstExprSerializationError(this.message);
 
   @override
   String toString() => message;
 }