A small utility which adds a Unity event for preprocessing scene saves.

gistfile1.txt

using UnityEngine;
using UnityEditor;
using System;
using System.Collections.Generic;

public class AssetSaveProcess : AssetModificationProcessor
{
	public static event Action OnSaveCurrentScene;

	public static string[] OnWillSaveAssets (string[] paths)
	{
		bool savingCurrentScene = false;
		for(int i = 0; i < paths.Length; i++)
		{
			var path = paths[i];

			if(path == EditorApplication.currentScene)
			{
				savingCurrentScene = true;
			}
		}

		if(savingCurrentScene)
		{
			if(OnSaveCurrentScene != null)
			{
				OnSaveCurrentScene();
			}
		}
		
		return paths;
	}
}