Create pkg/front_end/src/base and begin populating with general use classes.

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 'dart:developer';
 
 import 'package:analyzer/error/error.dart' show AnalysisError;
 import 'package:analyzer/exception/exception.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_general.dart';
 import 'package:analyzer/src/task/driver.dart';
 import 'package:analyzer/src/task/model.dart';
+import 'package:front_end/src/base/analysis_target.dart';
+
+export 'package:front_end/src/base/analysis_target.dart' show AnalysisTarget;
 
 /**
  * A function that converts the given [key] and [value] into a [TaskInput].
  */
 typedef TaskInput<E> BinaryFunction<K, V, E>(K key, V value);
 
 /**
  * A function that takes an analysis [context] and an analysis [target] and
  * returns an analysis task. Such functions are passed to a [TaskDescriptor] to
  * be used to create the described task.
@@ skipping 34 matching lines @@
   AnalysisContextTarget(this.context);
 
   @override
   Source get librarySource => null;
 
   @override
   Source get source => null;
 }
 
 /**
- * An object with which an analysis result can be associated.
- *
- * Clients may implement this class when creating new kinds of targets.
- * Instances of this type are used in hashed data structures, so subtypes are
- * required to correctly implement [==] and [hashCode].
- */
-abstract class AnalysisTarget {
-  /**
-   * If this target is associated with a library, return the source of the
-   * library's defining compilation unit; otherwise return `null`.
-   */
-  Source get librarySource;
-
-  /**
-   * Return the source associated with this target, or `null` if this target is
-   * not associated with a source.
-   */
-  Source get source;
-}
-
-/**
  * An object used to compute one or more analysis results associated with a
  * single target.
  *
  * Clients must extend this class when creating new tasks.
  */
 abstract class AnalysisTask {
   /**
    * A queue storing the last 10 task descriptions for diagnostic purposes.
    */
   static final LimitedQueue<String> LAST_TASKS = new LimitedQueue<String>(10);
@@ skipping 693 matching lines @@
   /**
    * A work should be done, but without any special urgency.
    */
   NORMAL,
 
   /**
    * Nothing to do.
    */
   NONE
 }