Fix service isolate initialization in PRODUCT mode.

runtime/lib/vmservice.cc

Index: runtime/lib/vmservice.cc
diff --git a/runtime/lib/vmservice.cc b/runtime/lib/vmservice.cc
index 253bcfad718719e1d357063b2e825dcbfeabb8ec..9d83c13b9d8e421a7bb7b734f77843d561c7e655 100644
--- a/runtime/lib/vmservice.cc
+++ b/runtime/lib/vmservice.cc
@@ -130,15 +130,15 @@ DEFINE_NATIVE_ENTRY(VMService_SendObjectRootServiceMessage, 1) {
 
 
 DEFINE_NATIVE_ENTRY(VMService_OnStart, 0) {
-#ifndef PRODUCT
-  if (!FLAG_support_service) {
-    return Object::null();
-  }
   if (FLAG_trace_service) {
     OS::Print("vm-service: Booting dart:vmservice library.\n");
   }
   // Boot the dart:vmservice library.
   ServiceIsolate::BootVmServiceLibrary();
+  if (!FLAG_support_service) {
+    return Object::null();
+  }
+#ifndef PRODUCT
   // Register running isolates with service.
   RegisterRunningIsolatesVisitor register_isolates(thread);
   if (FLAG_trace_service) {