Use "Object" as the reified type of covariant override parameters.

pkg/dev_compiler/test/codegen_test.dart

 // Copyright (c) 2016, 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.
 
 /// Tests code generation.
 ///
 /// Runs Dart Dev Compiler on all input in the `codegen` directory and checks
 /// that the output is what we expected.
 library dev_compiler.test.codegen_test;
 
@@ skipping 71 matching lines @@
   var sharedCompiler = new ModuleCompiler(new AnalyzerOptions.basic(
       dartSdkSummaryPath: sdkSummaryFile, summaryPaths: summaryPaths));
 
   var testDirs = [
     'language',
     'corelib',
     path.join('corelib', 'regexp'),
     path.join('lib', 'collection'),
     path.join('lib', 'convert'),
     path.join('lib', 'html'),
-    // TODO(vsm): Fix these - they import files from a different directory
-    // - this triggers an invalid library root build error.
-    // path.join('lib', 'html', 'custom'),
     path.join('lib', 'math'),
     path.join('lib', 'mirrors'),
     path.join('lib', 'typed_data'),
   ];
 
   // Copy all of the test files and expanded multitest files to
   // gen/codegen_tests. We'll compile from there.
   var testFiles = _setUpTests(testDirs);
 
   // Our default compiler options. Individual tests can override these.
@@ skipping 151 matching lines @@
   var testFiles = <String>[];
 
   for (var testDir in testDirs) {
     // Look for the tests in the "_strong" directories in the SDK's main
     // "tests" directory.
     var dirParts = path.split(testDir);
     var sdkTestDir =
         path.join(dirParts[0] + "_strong", path.joinAll(dirParts.skip(1)));
     var inputPath = path.join(testDirectory, '../../../tests/', sdkTestDir);
 
-    for (var file in _listFiles(inputPath, recursive: false)) {
+    for (var file in _listFiles(inputPath, recursive: true)) {
       var relativePath = path.relative(file, from: inputPath);
       var outputPath = path.join(codegenTestDir, testDir, relativePath);
 
       _ensureDirectory(path.dirname(outputPath));
 
       // Copy it over. We do this even for multitests because import_self_test
       // is a multitest, yet imports its own unexpanded form (!).
       new File(file).copySync(outputPath);
 
       if (file.endsWith("_test.dart")) {
@@ skipping 107 matching lines @@
   'language/mixin_illegal_syntax_test_04_multi',
   'language/mixin_illegal_syntax_test_05_multi',
   'language/mixin_illegal_syntax_test_06_multi',
   'language/mixin_illegal_syntax_test_07_multi',
   'language/mixin_illegal_syntax_test_08_multi',
   'language/mixin_illegal_syntax_test_09_multi',
   'language/mixin_illegal_syntax_test_10_multi',
   'language/mixin_illegal_syntax_test_11_multi',
   'language/mixin_illegal_syntax_test_12_multi',
   'language/mixin_illegal_syntax_test_13_multi',
-  'language/mixin_illegal_syntax_test_14_multi'
+  'language/mixin_illegal_syntax_test_14_multi',
+
+  // TODO(vsm): Fix these - they import files from a different directory
+  // - this triggers an invalid library root build error.
+  'lib/html/custom/attribute_changed_callback_test',
+  'lib/html/custom/entered_left_view_test',
+  'lib/html/custom/js_custom_test',
+  'lib/html/custom/mirrors_test',
+  'lib/html/custom/regress_194523002_test',
 ]);