Add --hot-reload-rollback test mode

tools/testing/dart/test_suite.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Classes and methods for enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 282 matching lines @@
     int shards = configuration['shards'];
     if (shards > 1 && testCase.hash % shards != configuration['shard'] - 1) {
       return;
     }
     // Test if the selector includes this test.
     RegExp pattern = configuration['selectors'][suiteName];
     if (!pattern.hasMatch(testCase.displayName)) {
       return;
     }
 
-    if (configuration['hot_reload']) {
+    if (configuration['hot_reload'] || configuration['hot_reload_rollback']) {
       // Handle reload special cases.
       if (expectations.contains(Expectation.COMPILETIME_ERROR)) {
         // Running a test that expects a compilation error with hot reloading
         // is redundant with a regular run of the test.
         return;
       }
     }
 
     // Update Summary report
     if (configuration['report']) {
@@ skipping 529 matching lines @@
     Path filePath = new Path(filename);
 
     var optionsFromFile = readOptionsFromFile(filePath);
     CreateTest createTestCase = makeTestCaseCreator(optionsFromFile);
 
     if (optionsFromFile['isMultitest']) {
       group.add(doMultitest(filePath,
                             buildDir,
                             suiteDir,
                             createTestCase,
-                            configuration['hot_reload']));
+                            (configuration['hot_reload'] ||
+                             configuration['hot_reload_rollback'])));
     } else {
       createTestCase(filePath, filePath, optionsFromFile['hasCompileError'],
           optionsFromFile['hasRuntimeError'],
           hasStaticWarning: optionsFromFile['hasStaticWarning']);
     }
   }
 
   static Path _findPubspecYamlFile(Path filePath) {
     final existsCache = TestUtils.existsCache;
 
@@ skipping 1619 matching lines @@
       }
       if (path.length > WINDOWS_SHORTEN_PATH_LIMIT) {
         ++shortNameCounter;
         var pathEnd = path.substring(path.length - WINDOWS_PATH_END_LENGTH);
         path = "short${shortNameCounter}_$pathEnd";
       }
     }
     return path;
   }
 }