Move notification of isolate creation until after the ObjectStore is initialized.

runtime/vm/debugger.cc

Index: runtime/vm/debugger.cc
diff --git a/runtime/vm/debugger.cc b/runtime/vm/debugger.cc
index 226eeb9033ab9e836369682e5d05be420b8b3e4e..b180e9675865d6583d51ce182e3fa095708fb8c1 100644
--- a/runtime/vm/debugger.cc
+++ b/runtime/vm/debugger.cc
@@ -2240,7 +2240,10 @@ void Debugger::Initialize(Isolate* isolate) {
   // debugger wire protocol messages.
   isolate_id_ = isolate->main_port();
   initialized_ = true;
+}
+
 
+void Debugger::NotifyIsolateCreated() {
   // Signal isolate creation event.
   SignalIsolateEvent(DebuggerEvent::kIsolateCreated);
 }