VM eventhandler: Update epoll/kqueue even if the only event is an error

runtime/bin/eventhandler_fuchsia.cc

Index: runtime/bin/eventhandler_fuchsia.cc
diff --git a/runtime/bin/eventhandler_fuchsia.cc b/runtime/bin/eventhandler_fuchsia.cc
index 043e95ee189326a86aad4228da8e354f53ea5246..6531ce5bc6b9485be6fb3b03e99c8080d4f81039 100644
--- a/runtime/bin/eventhandler_fuchsia.cc
+++ b/runtime/bin/eventhandler_fuchsia.cc
@@ -389,14 +389,12 @@ void EventHandlerImplementation::HandleEvents(struct epoll_event* events,
       DescriptorInfo* di =
           reinterpret_cast<DescriptorInfo*>(events[i].data.ptr);
       const intptr_t old_mask = di->Mask();
-      intptr_t event_mask = GetPollEvents(events[i].events, di);
+      const intptr_t event_mask = GetPollEvents(events[i].events, di);
+      LOG_INFO("HandleEvents: fd=%ld events=%ld\n", di->fd(), event_mask);
       if ((event_mask & (1 << kErrorEvent)) != 0) {
         di->NotifyAllDartPorts(event_mask);
-      }
-      event_mask &= ~(1 << kErrorEvent);
-
-      LOG_INFO("HandleEvents: fd=%ld events=%ld\n", di->fd(), event_mask);
-      if (event_mask != 0) {
+        UpdateEpollInstance(old_mask, di);
+      } else if (event_mask != 0) {
         Dart_Port port = di->NextNotifyDartPort(event_mask);
         ASSERT(port != 0);
         UpdateEpollInstance(old_mask, di);