Improve 'length' instance property reference encoding.

pkg/analyzer/tool/summary/idl.dart

 // Copyright (c) 2015, 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.
 
 /**
  * This file is an "idl" style description of the summary format.  It is not
  * executed directly; instead it is parsed and transformed into code that
  * implements the summary format.
  *
  * The code generation process introduces the following non-typical semantics:
@@ skipping 288 matching lines @@
    * The entity is a static const field.
    */
   constField,
 
   /**
    * The entity is a static method.
    */
   staticMethod,
 
   /**
+   * The `length` property access.
+   */
+  length,
+
+  /**
    * The entity is a typedef.
    */
   typedef,
 
   /**
    * The entity is a top level function.
    */
   topLevelFunction,
 
   /**
@@ skipping 1139 matching lines @@
   int propagatedTypeSlot;
 
   /**
    * If this variable is inferrable, nonzero slot id identifying which entry in
    * [LinkedLibrary.types] contains the inferred type for this variable.  If
    * there is no matching entry in [LinkedLibrary.types], then no type was
    * inferred for this variable, so its static type is `dynamic`.
    */
   int inferredTypeSlot;
 }