Service isolate rework take 2

runtime/bin/vmservice/vmservice_io.dart

Index: runtime/bin/vmservice/vmservice_io.dart
diff --git a/runtime/bin/vmservice/vmservice_io.dart b/runtime/bin/vmservice/vmservice_io.dart
index c04d485dbf27a20b724cdf7187ad3f6d4f45f5f9..2d99e17eb85787fab4fe322e4732688083870545 100644
--- a/runtime/bin/vmservice/vmservice_io.dart
+++ b/runtime/bin/vmservice/vmservice_io.dart
@@ -10,6 +10,7 @@ import 'dart:io';
 import 'dart:isolate';
 import 'dart:vmservice';
 
+part 'loader.dart';
 part 'resources.dart';
 part 'server.dart';
 
@@ -21,6 +22,8 @@ bool _autoStart;
 
 bool _isWindows = false;
 
+var _signalWatch;
+
 // HTTP servr.
 Server server;
 Future<Server> serverFuture;
@@ -54,18 +57,27 @@ void _onSignal(ProcessSignal signal) {
   }
 }
 
-void _registerSignalHandler(Stream signalWatch(ProcessSignal signal)) {
+void _registerSignalHandler() {
   if (_isWindows) {
     // Cannot register for signals on Windows.
     return;
   }
-  signalWatch(ProcessSignal.SIGQUIT).listen(_onSignal);
+  _signalWatch(ProcessSignal.SIGQUIT).listen(_onSignal);
 }
 
-main(Stream signalWatch(ProcessSignal signal)) {
+const _shortDelay = const Duration(milliseconds: 10);
+
+main() {
   if (_autoStart) {
     _bootServer();
     server.startup();
+    // It's just here to push an event on the event loop so that we invoke the
+    // scheduled microtasks.
+    Timer.run(() {});
   }
-  _registerSignalHandler(signalWatch);
+  scriptLoadPort.handler = _processLoadRequest;
+  // Register signal handler after a small delay to avoid stalling main
+  // isolate startup.
+  new Timer(_shortDelay, _registerSignalHandler);
+  return scriptLoadPort;
 }