Improve test script help output for --compiler

tools/testing/dart/test_options.dart

 // Copyright (c) 2013, 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 test_options_parser;
 
 import "dart:io";
 import "drt_updater.dart";
 import "test_suite.dart";
 import "path.dart";
@@ skipping 45 matching lines @@
    */
   TestOptionsParser() {
     _options = [
       new _TestOptionSpecification('mode', 'Mode in which to run the tests',
           ['-m', '--mode'], ['all', 'debug', 'release', 'product'], 'debug'),
       new _TestOptionSpecification(
           'compiler',
           '''Specify any compilation step (if needed).
 
    none: Do not compile the Dart code (run native Dart code on the VM).
-         (only valid with the following runtimes: vm, flutter, drt)
+          (only valid with the following runtimes: vm, flutter, drt)
+
+   precompiler: Compile into AOT snapshot before running the test.
+          (only valid with the dart_precompiled runtime)
 
    dart2js: Compile dart code to JavaScript by running dart2js.
-         (only valid with the following runtimes: d8, drt, chrome,
-         safari, ie9, ie10, ie11, firefox, opera, chromeOnAndroid,
-         none (compile only)),
+          (only valid with the following runtimes: d8, drt, chrome,
+          safari, ie9, ie10, ie11, firefox, opera, chromeOnAndroid,
+          none (compile only)),
 
    dart2analyzer: Perform static analysis on Dart code by running the analyzer
           (only valid with the following runtimes: none)
 
-   dart2app:
-   dart2appjit: Compile the Dart code into an app snapshot before running test
+   app_jit: Compile the Dart code into an app snapshot before running test
           (only valid with dart_app runtime)
 
    dartk: Compile the Dart source into Kernel before running test.
 
    dartkp: Compiler the Dart source into Kernel and then Kernel into AOT
-   snapshot before running the test.''',
+          snapshot before running the test.
+          (only valid with the dart_precompiled runtime)
+          ''',
           ['-c', '--compiler'],
           [
             'none',
             'precompiler',
             'dart2js',
             'dart2analyzer',
             'app_jit',
             'dartk',
             'dartkp'
           ],
@@ skipping 906 matching lines @@
         return option;
       }
     }
     print('Unknown test option $name');
     exit(1);
     return null; // Unreachable.
   }
 
   List<_TestOptionSpecification> _options;
 }