Move exception support to its own library

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/exception/exception.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart' show AnalysisError;
-import 'package:analyzer/src/generated/java_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';
 
 /**
  * A function that converts the given [key] and [value] into a [TaskInput].
  */
 typedef TaskInput<E> BinaryFunction<K, V, E>(K key, V value);
 
@@ skipping 254 matching lines @@
             // This edge is in a cycle (or leads to a cycle) so add it to the
             // path
             path.add(result);
             return true;
           }
         }
       }
       // There was no cycle.
       return false;
     }
+
     if (cycle.length > 0) {
       traverse(cycle[0]);
     }
     return path;
   }
 
   /**
    * Perform this analysis task, ensuring that all exceptions are wrapped in an
    * [AnalysisException].
    *
@@ skipping 497 matching lines @@
   /**
    * A work should be done, but without any special urgency.
    */
   NORMAL,
 
   /**
    * Nothing to do.
    */
   NONE
 }