Add --hot-reload to the test harness.

tools/testing/dart/test_options.dart

Index: tools/testing/dart/test_options.dart
diff --git a/tools/testing/dart/test_options.dart b/tools/testing/dart/test_options.dart
index 7f44f3cc65c61f18672ed801b05efc647ea1763a..da2c5d047424cead0c942522fba094cff324362f 100644
--- a/tools/testing/dart/test_options.dart
+++ b/tools/testing/dart/test_options.dart
@@ -187,8 +187,12 @@ class TestOptionsParser {
           'noopt', 'Run an in-place precompilation', ['--noopt'], [], false,
           type: 'bool'),
       new _TestOptionSpecification(
-          'use_blobs', 'Use mmap instead of shared libraries for precompilation', ['--use-blobs'], [], false,
-          type: 'bool'),
+          'hot_reload', 'Run hot reload stress tests', ['--hot-reload'], [],
+          false, type: 'bool'),
+      new _TestOptionSpecification(
+          'use_blobs',
+          'Use mmap instead of shared libraries for precompilation',
+          ['--use-blobs'], [], false, type: 'bool'),
       new _TestOptionSpecification(
           'timeout', 'Timeout in seconds', ['-t', '--timeout'], [], -1,
           type: 'int'),