Fix vmservice shutdown hang

runtime/vm/service_isolate.cc

Index: runtime/vm/service_isolate.cc
diff --git a/runtime/vm/service_isolate.cc b/runtime/vm/service_isolate.cc
index a067c4e6cc5a43a4baf708ed0a932383088aa7a8..3350583b7cb794f90243b16f34c6819a5cd4b0c9 100644
--- a/runtime/vm/service_isolate.cc
+++ b/runtime/vm/service_isolate.cc
@@ -549,6 +549,9 @@ void ServiceIsolate::BootVmServiceLibrary() {
   const Object& result = Object::Handle(
       DartEntry::InvokeFunction(boot_function, Object::empty_array()));
   ASSERT(!result.IsNull());
+  if (result.IsUnwindError() || result.IsUnhandledException()) {
+    Exceptions::PropagateError(Error::Cast(result));
+  }
   Dart_Port port = ILLEGAL_PORT;
   if (result.IsReceivePort()) {
     port = ReceivePort::Cast(result).Id();