Enable debugging from a single console.

dart/tools/ddbg.dart

Index: dart/tools/ddbg.dart
diff --git a/dart/tools/ddbg.dart b/dart/tools/ddbg.dart
index eaf0258a85f979918ea8fe8cd6595f4997207707..8af5714559008d11326344d91e0fbcd3bf90da01 100644
--- a/dart/tools/ddbg.dart
+++ b/dart/tools/ddbg.dart
@@ -526,7 +526,7 @@ int jsonObjectLength(String string) {
 }
 
 
-void main() {
+void debuggerMain() {
   outstandingCommands = new Map<int, Completer>();
   vmSock = new Socket("127.0.0.1", 5858);
   vmStream = new SocketOutputStream(vmSock);
@@ -548,3 +548,26 @@ void main() {
     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();
+  }
+}