Do not JSON encode the 'result' of a service rpc.

runtime/vm/service_event.cc

Index: runtime/vm/service_event.cc
diff --git a/runtime/vm/service_event.cc b/runtime/vm/service_event.cc
index 3dfe66b793cf4506d68579b4ff25a93125bc5427..c1be69047f8ce418d0ac75e603eef32c2fb38fd6 100644
--- a/runtime/vm/service_event.cc
+++ b/runtime/vm/service_event.cc
@@ -36,7 +36,8 @@ ServiceEvent::ServiceEvent(const DebuggerEvent* debugger_event)
       type_(TranslateEventType(debugger_event->type())),
       breakpoint_(NULL),
       top_frame_(NULL),
-      exception_(NULL) {
+      exception_(NULL),
+      gc_stats_(NULL) {
   DebuggerEvent::EventType type = debugger_event->type();
   if (type == DebuggerEvent::kBreakpointReached) {
     set_breakpoint(debugger_event->breakpoint());
@@ -78,6 +79,8 @@ const char* ServiceEvent::EventTypeToCString(EventType type) {
       return "BreakpointResolved";
     case kBreakpointRemoved:
       return "BreakpointRemoved";
+    case kGC:
+      return "GC";  // TODO(koda): Change to GarbageCollected.
     default:
       UNREACHABLE();
       return "Unknown";
@@ -100,6 +103,11 @@ void ServiceEvent::PrintJSON(JSONStream* js) const {
   if (exception() != NULL) {
     jsobj.AddProperty("exception", *(exception()));
   }
+  if (gc_stats() != NULL) {
+    jsobj.AddProperty("reason", Heap::GCReasonToString(gc_stats()->reason_));
+    isolate()->heap()->PrintToJSONObject(Heap::kNew, &jsobj);
+    isolate()->heap()->PrintToJSONObject(Heap::kOld, &jsobj);
+  }
 }
 
 }  // namespace dart