Add --hot-reload-test-mode flag to embedder and wire it up to test.py

tools/testing/dart/compiler_configuration.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.
 
 library compiler_configuration;
 
 import 'dart:io' show Platform;
 
 import 'runtime_configuration.dart' show RuntimeConfiguration;
 
@@ skipping 161 matching lines @@
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     List<String> args = [];
     if (isChecked) {
       args.add('--enable_asserts');
       args.add('--enable_type_checks');
     }
     if (hotReload) {
-      args.add('--identity-reload');
-      args.add('--reload-every=100000');
+      args.add('--hot-reload-test-mode');
+      // Remove the following once known bugs with background compilation
+      // and OSR are fixed.
       args.add('--no-background-compilation');
       args.add('--no-osr');
     }
     return args
       ..addAll(vmOptions)
       ..addAll(sharedOptions)
       ..addAll(originalArguments);
   }
 }
 
@@ skipping 457 matching lines @@
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     return <String>[];
   }
 }