Move exception support to its own library

pkg/analyzer/test/src/task/manager_test.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.test.src.task.manager_test;
 
-import 'package:analyzer/src/generated/java_engine.dart';
+import 'package:analyzer/exception/exception.dart';
 import 'package:analyzer/src/task/manager.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../generated/test_support.dart';
 import '../../utils.dart';
 
 main() {
   initializeTestEnvironment();
@@ skipping 105 matching lines @@
   test_removePriorityResult_present() {
     TaskManager manager = new TaskManager();
     manager.addPriorityResult(result1);
     manager.addPriorityResult(result2);
     Set<ResultDescriptor> results = manager.priorityResults;
     expect(results, unorderedEquals([result1, result2]));
     manager.removePriorityResult(result1);
     expect(results, unorderedEquals([result2]));
   }
 }