Simplify 0-timers to not go through the eventhandler.

runtime/bin/eventhandler.cc

Index: runtime/bin/eventhandler.cc
diff --git a/runtime/bin/eventhandler.cc b/runtime/bin/eventhandler.cc
index 8de036eb8bf0acb18526cf6b6ebe847c450b67e2..3a86b2fd7c95e3b30e7d8e87ad535dbb029a4cd3 100644
--- a/runtime/bin/eventhandler.cc
+++ b/runtime/bin/eventhandler.cc
@@ -96,7 +96,12 @@ void FUNCTION_NAME(EventHandler_SendData)(Dart_NativeArguments args) {
   Dart_Port dart_port =
       DartUtils::GetIntegerField(handle, DartUtils::kIdFieldName);
   int64_t data = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 2));
-  event_handler->SendData(id, dart_port, data);
+  if (id == kTimerId && data == 0) {
+    // This is a 0-timer. Simply queue a 'null' on the port.
+    DartUtils::PostNull(dart_port);
+  } else {
+    event_handler->SendData(id, dart_port, data);
+  }
 }
 
 }  // namespace bin