Add new Dart API call Dart_MakeIsolateRunnable(). This would allow an

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
===================================================================
--- runtime/vm/dart_api_impl.cc	(revision 20976)
+++ runtime/vm/dart_api_impl.cc	(working copy)
@@ -938,6 +938,16 @@
 }
 
 
+DART_EXPORT bool Dart_IsolateMakeRunnable(Dart_Isolate isolate) {
+  CHECK_NO_ISOLATE(Isolate::Current());
+  if (isolate == NULL) {
+    FATAL1("%s expects argument 'isolate' to be non-null.",  CURRENT_FUNC);
+  }
+  Isolate* iso = reinterpret_cast<Isolate*>(isolate);
+  return iso->MakeRunnable();
+}
+
+
 // --- Messages and Ports ---
 
 DART_EXPORT void Dart_SetMessageNotifyCallback(