Add Dart_PostPriority function to dart_api, and use it in runAsync to schedule immediate events in …

runtime/bin/builtin_natives.cc

Index: runtime/bin/builtin_natives.cc
diff --git a/runtime/bin/builtin_natives.cc b/runtime/bin/builtin_natives.cc
index 48c10fbd8592f80c3461ddb0c1cfe648f918835f..b0b7f430a33b8aaa9c07dedfaaca850ff2f8d48a 100644
--- a/runtime/bin/builtin_natives.cc
+++ b/runtime/bin/builtin_natives.cc
@@ -63,6 +63,7 @@ namespace bin {
   V(FileSystemWatcher_ReadEvents, 1)                                           \
   V(FileSystemWatcher_UnwatchPath, 1)                                          \
   V(FileSystemWatcher_WatchPath, 4)                                            \
+  V(DartAPI_SendPriority, 2)                                                   \
   V(Logger_PrintString, 1)
 
 BUILTIN_NATIVE_LIST(DECLARE_FUNCTION);
@@ -115,5 +116,14 @@ void FUNCTION_NAME(Logger_PrintString)(Dart_NativeArguments args) {
   }
 }
 
+
+void FUNCTION_NAME(DartAPI_SendPriority)(Dart_NativeArguments args) {
+  Dart_Handle port = Dart_GetNativeArgument(args, 0);
+  Dart_Handle msg = Dart_GetNativeArgument(args, 1);
+  Dart_Handle id = Dart_GetField(port, DartUtils::NewString("_id"));
+  Dart_Port port_id = DartUtils::GetIntegerValue(id);
+  Dart_PostPriority(port_id, msg);
+}
+
 }  // namespace bin
 }  // namespace dart