Remove legacy restart code

runtime/lib/vmservice.cc

Index: runtime/lib/vmservice.cc
diff --git a/runtime/lib/vmservice.cc b/runtime/lib/vmservice.cc
index ad4e0fa6a1c1a1b98360d2477f9ea8484b9c8922..7753bc9cbcd937664da8821e20071b0eaf0a6de3 100644
--- a/runtime/lib/vmservice.cc
+++ b/runtime/lib/vmservice.cc
@@ -122,7 +122,7 @@ DEFINE_NATIVE_ENTRY(VMService_SendIsolateServiceMessage, 2) {
 DEFINE_NATIVE_ENTRY(VMService_SendRootServiceMessage, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(Array, message, arguments->NativeArgAt(0));
   if (FLAG_support_service) {
-    Service::HandleRootMessage(message);
+    return Service::HandleRootMessage(message);
   }
   return Object::null();
 }
@@ -131,7 +131,7 @@ DEFINE_NATIVE_ENTRY(VMService_SendRootServiceMessage, 1) {
 DEFINE_NATIVE_ENTRY(VMService_SendObjectRootServiceMessage, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(Array, message, arguments->NativeArgAt(0));
   if (FLAG_support_service) {
-    Service::HandleObjectRootMessage(message);
+    return Service::HandleObjectRootMessage(message);
   }
   return Object::null();
 }