Properly split dart:_vmservice across sdk and runtime

sdk/lib/vmservice/vmservice.dart

Index: sdk/lib/vmservice/vmservice.dart
diff --git a/runtime/lib/vmservice/vmservice.dart b/sdk/lib/vmservice/vmservice.dart
similarity index 96%
rename from runtime/lib/vmservice/vmservice.dart
rename to sdk/lib/vmservice/vmservice.dart
index 3c66673731d15fd3ff931823071355d469643396..54388cdc7f3602a7d59292a9d2091e5f03af7433 100644
--- a/runtime/lib/vmservice/vmservice.dart
+++ b/sdk/lib/vmservice/vmservice.dart
@@ -1,8 +1,8 @@
-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2015, 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 vmservice;
+library dart._vmservice;
 
 import 'dart:async';
 import 'dart:convert';
@@ -322,10 +322,11 @@ void _registerIsolate(int port_id, SendPort sp, String name) {
   service.runningIsolates.isolateStartup(port_id, sp, name);
 }
 
-void _onStart() native "VMService_OnStart";
+external void _onStart();
 
-void _onExit() native "VMService_OnExit";
+external void _onExit();
 
-bool _vmListenStream(String streamId) native "VMService_ListenStream";
+external bool _vmListenStream(String streamId);
+
+external void _vmCancelStream(String streamId);
 
-void _vmCancelStream(String streamId) native "VMService_CancelStream";