Fix vmservice shutdown hang

runtime/vm/service_isolate.cc

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/service_isolate.h"
 
 #include "vm/compiler.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/isolate.h"
@@ skipping 531 matching lines @@
   const Library& vmservice_library =
       Library::Handle(Library::LookupLibrary(thread, Symbols::DartVMService()));
   ASSERT(!vmservice_library.IsNull());
   const String& boot_function_name = String::Handle(String::New("boot"));
   const Function& boot_function = Function::Handle(
       vmservice_library.LookupFunctionAllowPrivate(boot_function_name));
   ASSERT(!boot_function.IsNull());
   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();
   }
   ASSERT(port != ILLEGAL_PORT);
   ServiceIsolate::SetServicePort(port);
 }
 
 
 void ServiceIsolate::VisitObjectPointers(ObjectPointerVisitor* visitor) {}
 
 }  // namespace dart