Make VM service id handling JSON-RPC 2 compliant.

runtime/vm/json_stream.h

Index: runtime/vm/json_stream.h
diff --git a/runtime/vm/json_stream.h b/runtime/vm/json_stream.h
index d314dbf62eae1cafa5bb861be4d802132fafca61..65cce171fb7bb8f7d9347b32dbb5dfbe11788854 100644
--- a/runtime/vm/json_stream.h
+++ b/runtime/vm/json_stream.h
@@ -57,7 +57,7 @@ class JSONStream : ValueObject {
 
   void Setup(Zone* zone,
              Dart_Port reply_port,
-             const String& seq,
+             const Instance& seq,
              const String& method,
              const Array& param_keys,
              const Array& param_values);
@@ -100,7 +100,7 @@ class JSONStream : ValueObject {
   // otherwise.
   bool ParamIs(const char* key, const char* value) const;
 
-  const char* seq() const { return seq_; }
+  RawInstance* seq() const { return seq_; }
   const char* method() const { return method_; }
   const char** param_keys() const { return param_keys_; }
   const char** param_values() const { return param_values_; }
@@ -171,7 +171,7 @@ class JSONStream : ValueObject {
   RingServiceIdZone default_id_zone_;
   ServiceIdZone* id_zone_;
   Dart_Port reply_port_;
-  const char* seq_;
+  RawInstance* seq_;

[Cutch, 2015/07/27 14:00:51]

You need to store seq_ as an Instance&.

[nweiz, 2015/07/27 18:16:02]

I'm pretty out of my depth here. If I do this, it seems like assigning to seq_
in Setup fails because Instance::operator= is private.

   const char* method_;
   const char** param_keys_;
   const char** param_values_;