Use AnalysisOptions.signature as a way to check compatibility.

pkg/analyzer/lib/src/generated/package.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 analyzer.src.generated.package;
 
 import 'dart:collection';
 
 import 'package:analyzer/exception/exception.dart';
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 140 matching lines @@
   /**
    * Initialize a newly create package description to describe the package with
    * the given [id] that is being analyzed against the given [sdk] using the
    * given [options].
    */
   PackageDescription(this.id, this.sdk, this.options);
 
   @override
   int get hashCode {
     int hashCode = 0;
-    for (int value in options.encodeCrossContextOptions()) {
+    for (int value in options.signature) {
       hashCode = JenkinsSmiHash.combine(hashCode, value);
     }
     hashCode = JenkinsSmiHash.combine(hashCode, id.hashCode);
     hashCode = JenkinsSmiHash.combine(hashCode, sdk.hashCode);
     return JenkinsSmiHash.finish(hashCode);
   }
 
   @override
   bool operator ==(Object other) {
     return other is PackageDescription &&
         other.sdk == sdk &&
-        AnalysisOptions.crossContextOptionsEqual(
-            other.options.encodeCrossContextOptions(),
-            options.encodeCrossContextOptions()) &&
+        AnalysisOptions.signaturesEqual(
+            other.options.signature, options.signature) &&
         other.id == id;
   }
 }
 
 /**
  * Manages the contexts in which each package is analyzed.
  */
 class PackageManager {
   /**
    * The resource provider used to access the file system.
@@ skipping 48 matching lines @@
         finder.transitiveDependenciesFor(packageMap, packagePath);
     StringBuffer buffer = new StringBuffer();
     buffer.write(packagePath);
     for (String dependency in dependencies) {
       buffer.write(';');
       buffer.write(dependency);
     }
     return buffer.toString();
   }
 }