Fix a possible dead lock when quiting.

It could happen that we are quitting when the embed thread is still
waiting for the main thread, so we make sure embed thread is always
signaled when quitting.

common/node_bindings.cc

@@ -39,10 +39,16 @@ NodeBindings::NodeBindings(bool is_browser)
 }
 
 NodeBindings::~NodeBindings() {
-  // Clear uv.
+  // Quit the embed thread.
   embed_closed_ = true;
+  uv_sem_post(&embed_sem_);
   WakeupEmbedThread();
+
+  // Wait for everything to be done.
   uv_thread_join(&embed_thread_);
+  message_loop_->RunUntilIdle();
+
+  // Clear uv.
   uv_sem_destroy(&embed_sem_);
   uv_timer_stop(&idle_timer_);
 }