When a project with a large number of Prefabs, which have many scripts, is fully imported, and the Editor is restarted, there is a long wait where the Editor spends booting up.

After debugging a user project, we could see that a lot of time was being spent inside of GetPrefabDynamicDependencies.

This was an issue not because of GetPrefabDynamicDependencies being slow, but due to the fact that thousands of Prefabs were being marked as out of date and then this code was being run.

After further inspection, it was evident that the code which was matching the Prefab's custom dependencies was not matching.

This was due to the custom dependency being a script that had not been loaded as the categorization was happening during the InitialScriptRefresh which does not have a Domain with user code in it.

Expected: The Editor should start up quickly if there are not changes to assets.