Initial re-write of analysis context for the new task model

pkg/analyzer/lib/src/task/manager.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.src.task.manager;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/task/model.dart';
@@ skipping 49 matching lines @@
       List<TaskDescriptor> descriptors = taskMap[result];
       if (descriptors == null) {
         descriptors = <TaskDescriptor>[];
         taskMap[result] = descriptors;
       }
       descriptors.add(descriptor);
     });
   }
 
   /**
+   * Add the task descriptors in the given list of [descriptors] to the list of
+   * analysis task descriptors that can be used to compute analysis results.
+   */
+  void addTaskDescriptors(List<TaskDescriptor> descriptors) {
+    descriptors.forEach(addTaskDescriptor);
+  }
+
+  /**
    * Find a task that will compute the given [result] for the given [target].
    */
   TaskDescriptor findTask(AnalysisTarget target, ResultDescriptor result) {
     List<TaskDescriptor> descriptors = taskMap[result];
     if (descriptors == null) {
       throw new AnalysisException(
           'No tasks registered to compute $result for $target');
     }
     return _findBestTask(descriptors);
   }
@@ skipping 17 matching lines @@
   /**
    * Given a list of task [descriptors] that can be used to compute some
    * unspecified result, return the descriptor that will compute the result with
    * the least amount of work.
    */
   TaskDescriptor _findBestTask(List<TaskDescriptor> descriptors) {
     // TODO(brianwilkerson) Improve this implementation.
     return descriptors[0];
   }
 }