Fix incremental resolver to work with new task model

pkg/analyzer/lib/src/generated/incremental_resolver.dart

 // Copyright (c) 2014, 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 engine.incremental_resolver;
 
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'package:analyzer/src/context/cache.dart'
@@ skipping 818 matching lines @@
  */
 class IncrementalResolver {
   /**
    * The element of the compilation unit being resolved.
    */
   final CompilationUnitElementImpl _definingUnit;
 
   /**
    * The context the compilation unit being resolved in.
    */
-  AnalysisContextImpl _context;
+  AnalysisContext _context;
 
   /**
    * The object used to access the types from the core library.
    */
   TypeProvider _typeProvider;
 
   /**
    * The element for the library containing the compilation unit being resolved.
    */
   LibraryElementImpl _definingLibrary;
@@ skipping 1141 matching lines @@
   @override
   String toString() => name;
 }
 
 class _TokenPair {
   final _TokenDifferenceKind kind;
   final Token oldToken;
   final Token newToken;
   _TokenPair(this.kind, this.oldToken, this.newToken);
 }