Get memento objects from tasks, remember in cache and pass back to tasks.

pkg/analyzer/lib/task/model.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.
 
 library analyzer.task.model;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisTask;
 import 'package:analyzer/src/generated/java_engine.dart';
@@ skipping 85 matching lines @@
    * The target for which result values are being produced.
    */
   final AnalysisTarget target;
 
   /**
    * A table mapping input names to input values.
    */
   Map<String, dynamic> inputs;
 
   /**
+   * The optional data that the task associated with [target] last time.
+   * This data may help to compute outputs more efficiently.
+   */
+  dynamic inputMemento;
+
+  /**
    * A table mapping result descriptors whose values are produced by this task
    * to the values that were produced.
    */
   Map<ResultDescriptor, dynamic> outputs =
       new HashMap<ResultDescriptor, dynamic>();
 
   /**
+   * An optional data that the task wants to associate with [target].
+   * This data may help later to compute outputs more efficiently.
+   */
+  dynamic outputMemento;
+
+  /**
    * The exception that was thrown while performing this task, or `null` if the
    * task completed successfully.
    */
   CaughtException caughtException;
 
   /**
    * Initialize a newly created task to perform analysis within the given
    * [context] in order to produce results for the given [target].
    */
   AnalysisTask(this.context, this.target);
@@ skipping 259 matching lines @@
   /**
    * Return a list of the analysis results that will be computed by this task.
    */
   List<ResultDescriptor> get results;
 
   /**
    * Create and return a task that is described by this descriptor that can be
    * used to compute results based on the given [inputs].
    */
   AnalysisTask createTask(AnalysisContext context, AnalysisTarget target,
-      Map<String, dynamic> inputs);
+      Map<String, dynamic> inputs, dynamic inputMemento);
 }
 
 /**
  * A description of an input to an [AnalysisTask] that can be used to compute
  * that input.
  *
  * Clients are not expected to subtype this class.
  */
 abstract class TaskInput<V> {
   /**
@@ skipping 53 matching lines @@
    * be computed, or `false` if the inputs have been computed.
    *
    * It is safe to invoke [moveNext] after it has returned `false`. In this case
    * [moveNext] has no effect and will again return `false`.
    *
    * Throws a [StateError] if the value of the current result has not been
    * provided using [currentValue].
    */
   bool moveNext();
 }