Get more tests passing using the new task model

pkg/analyzer/test/generated/test_support.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.test_support;
 
 import 'dart:collection';
@@ skipping 533 matching lines @@
 
   @override
   void logInformation2(String message, Object exception) {
     infoCount++;
   }
 }
 
 class TestSource extends Source {
   String _name;
   String _contents;
-  int modificationStamp = 0;
+  int _modificationStamp = 0;
   bool exists2 = true;
 
   /**
    * A flag indicating whether an exception should be generated when an attempt
    * is made to access the contents of this source.
    */
   bool generateExceptionOnRead = false;
 
+  @override
+  int get modificationStamp => generateExceptionOnRead ? -1 : _modificationStamp;
+
   /**
    * The number of times that the contents of this source have been requested.
    */
   int readCount = 0;
 
   TestSource([this._name = '/test.dart', this._contents]);
 
   TimestampedData<String> get contents {
     readCount++;
     if (generateExceptionOnRead) {
@@ skipping 31 matching lines @@
   void getContentsToReceiver(Source_ContentReceiver receiver) {
     throw new UnsupportedOperationException();
   }
   Source resolve(String uri) {
     throw new UnsupportedOperationException();
   }
   Uri resolveRelativeUri(Uri uri) {
     return new Uri(scheme: 'file', path: _name).resolveUri(uri);
   }
   void setContents(String value) {
-    modificationStamp = new DateTime.now().millisecondsSinceEpoch;
+    generateExceptionOnRead = false;
+    _modificationStamp = new DateTime.now().millisecondsSinceEpoch;
     _contents = value;
   }
   @override
   String toString() => '$_name';
 }
 
 class TestSourceWithUri extends TestSource {
   final Uri uri;
 
   TestSourceWithUri(String path, this.uri, [String content])
@@ skipping 14 matching lines @@
     if (other is TestSource) {
       return other.uri == uri;
     }
     return false;
   }
 
   Uri resolveRelativeUri(Uri uri) {
     return this.uri.resolveUri(uri);
   }
 }