Emulate compiling a source file in the context of an existing library. Add --debugger-compile flag …

pkg/dev_compiler/web/main.dart

 #!/usr/bin/env 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.
 
 @JS()
 library dev_compiler.web.main;
 
 import 'dart:async';
 
 import 'package:args/command_runner.dart';
 import 'package:js/js.dart';
 
 import 'web_command.dart';
 
 @JS(r'$setUpDartDevCompilerInBrowser')
 external set setUpCompilerInBrowser(Function function);
 
 Future main() async {
-  var args = ['compile'];
+  var args = ['compile', '--repl-compile'];
   _runCommand(args);
 }
 
 /// Runs a single compile command, and returns an exit code.
 Future<int> _runCommand(List<String> args,
     {MessageHandler messageHandler}) async {
   try {
     // TODO: Remove CommandRunner and args if possible. May run into issues
     // with ArgResults or ArgParsers.
     var runner = new CommandRunner('dartdevc', 'Dart Development Compiler');
@@ skipping 23 matching lines @@
     // Anything else is likely a compiler bug.
     //
     // --unsafe-force-compile is a bit of a grey area, but it's nice not to
     // crash while compiling
     // (of course, output code may crash, if it had errors).
     //
     messageHandler("");
     messageHandler("We're sorry, you've found a bug in our compiler.");
     messageHandler("You can report this bug at:");
     messageHandler(
-      "    https://github.com/dart-lang/sdk/issues/labels/area-dev-compiler");
+        "    https://github.com/dart-lang/sdk/issues/labels/area-dev-compiler");
     messageHandler("");
     messageHandler(
         "Please include the information below in your report, along with");
     messageHandler(
         "any other information that may help us track it down. Thanks!");
     messageHandler("");
     messageHandler("    dartdevc arguments: " + args.join(' '));
     messageHandler("");
     messageHandler("```");
     messageHandler(error);
     messageHandler(stackTrace);
     messageHandler("```");
     return 70;
   }
 }