Make VM service id handling JSON-RPC 2 compliant.

runtime/vm/service.cc

 // Copyright (c) 2013, 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.
 
 #include "vm/service.h"
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 #include "platform/globals.h"
 
@@ skipping 491 matching lines @@
 void Service::InvokeMethod(Isolate* isolate, const Array& msg) {
   ASSERT(isolate != NULL);
   ASSERT(!msg.IsNull());
   ASSERT(msg.Length() == 6);
 
   {
     StackZone zone(isolate);
     HANDLESCOPE(isolate);
 
     Instance& reply_port = Instance::Handle(isolate);
-    String& seq = String::Handle(isolate);
+    Instance& seq = String::Handle(isolate);
     String& method_name = String::Handle(isolate);
     Array& param_keys = Array::Handle(isolate);
     Array& param_values = Array::Handle(isolate);
     reply_port ^= msg.At(1);
     seq ^= msg.At(2);
     method_name ^= msg.At(3);
     param_keys ^= msg.At(4);
     param_values ^= msg.At(5);
 
     ASSERT(!method_name.IsNull());
-    ASSERT(!seq.IsNull());
+    ASSERT(seq.IsNull() || seq.IsString() || seq.IsNumber());
     ASSERT(!param_keys.IsNull());
     ASSERT(!param_values.IsNull());
     ASSERT(param_keys.Length() == param_values.Length());
 
     if (!reply_port.IsSendPort()) {
       FATAL("SendPort expected.");
     }
 
     JSONStream js;
     js.Setup(zone.GetZone(), SendPort::Cast(reply_port).Id(),
@@ skipping 2532 matching lines @@
     ServiceMethodDescriptor& method = service_methods_[i];
     if (strcmp(method_name, method.name) == 0) {
       return &method;
     }
   }
   return NULL;
 }
 
 
 }  // namespace dart