Enable debugging from a single console.

dart/tools/ddbg.dart

 // Copyright (c) 2012, 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.
 
 // Simple interactive debugger shell that connects to the Dart VM's debugger
 // connection port.
 
 #import("dart:io");
 #import("dart:json");
 #import("dart:math", prefix: "Math");
@@ skipping 508 matching lines @@
       if (nexting == 0) return index;
     } else if (char == '"') {
       // Strings can contain braces. Skip their content.
       index = skipString(index);
     }
   }
   return 0;
 }
 
 
-void main() {
+void debuggerMain() {
   outstandingCommands = new Map<int, Completer>();
   vmSock = new Socket("127.0.0.1", 5858);
   vmStream = new SocketOutputStream(vmSock);
   var stdinStream = new StringInputStream(stdin);
   stdinStream.onLine = () {
     processCommand(stdinStream.readLine());
   };
   var vmInStream = new SocketInputStream(vmSock);
   vmInStream.onData = () {
     String s = decodeUtf8(vmInStream.read());
     processVmData(s);
   };
   vmInStream.onError = (err) {
     print("Error in debug connection: $err");
     quitShell();
   };
   vmInStream.onClosed = () {
     print("VM debugger connection closed");
     quitShell();
   };
 }
+
+void main() {
+  Options options = new Options();
+  List<String> arguments = options.arguments;
+  if (arguments.length > 0) {
+    arguments = <String>['--debug', '--verbose_debug']..addAll(arguments);
+    Process.start(options.executable, arguments).then((Process process) {
+      process.onExit = (int exitCode) {
+        print('${Strings.join(arguments, " ")} exited with $exitCode');
+      };
+      process.stdin.close();
+      // Redirecting both stdout and stderr of the child process to
+      // stdout.  This should help users keep track of which errors
+      // are coming from the debugger, and which errors are coming
+      // from the process being debugged.
+      process.stderr.pipe(stdout);
+      process.stdout.pipe(stdout);
+      debuggerMain();
+    });
+  } else {
+    debuggerMain();
+  }
+}