Use AnalysisOptions.signature as a way to check compatibility.

pkg/analyzer/lib/src/dart/analysis/driver.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.
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:typed_data';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart' show CompilationUnitElement;
@@ skipping 104 matching lines @@
 
   /**
    * The [SourceFactory] is used to resolve URIs to paths and restore URIs
    * from file paths.
    */
   SourceFactory _sourceFactory;
 
   /**
    * The salt to mix into all hashes used as keys for serialized data.
    */
-  final Uint32List _salt =
-      new Uint32List(1 + AnalysisOptions.crossContextOptionsLength);
+  final Uint32List _salt = new Uint32List(1 + AnalysisOptions.signatureLength);
 
   /**
    * The current file system state.
    */
   FileSystemState _fsState;
 
   /**
    * The combined unlinked and linked package for the SDK, extracted from
    * the given [sourceFactory].
    */
@@ skipping 676 matching lines @@
 
       return new _LibraryContext(library, store);
     });
   }
 
   /**
    * Fill [_salt] with data.
    */
   void _fillSalt() {
     _salt[0] = DATA_VERSION;
-    List<int> crossContextOptions =
-        _analysisOptions.encodeCrossContextOptions();
-    assert(crossContextOptions.length ==
-        AnalysisOptions.crossContextOptionsLength);
+    List<int> crossContextOptions = _analysisOptions.signature;
+    assert(crossContextOptions.length == AnalysisOptions.signatureLength);
     for (int i = 0; i < crossContextOptions.length; i++) {
       _salt[i + 1] = crossContextOptions[i];
     }
   }
 
   /**
    * Load the [AnalysisResult] for the given [file] from the [bytes]. Set
    * optional [content] and [resolvedUnit].
    */
   AnalysisResult _getAnalysisResultFromBytes(FileState file, List<int> bytes,
@@ skipping 758 matching lines @@
           libraryDeclarations.add(new TopLevelDeclarationInSource(
               file.source, declaration, isExported));
         }
       }
     }
 
     // We're not done yet.
     return false;
   }
 }