The error 'Recursive serialization is not allowed for threaded serialization' is thrown in the console when the BuildProfileContext instance is accessed and created/loaded in a serialization callback.

This was mentioned by a client here: http://supportstats.hq.unity3d.com/history.php?tid=1856204

Steps to reproduce:

1. Get shinai project from here: [https://github.cds.internal.unity3d.com/unity/shinai]

2. Add the attached script ([^CustomShaderPreprocessor.cs]) inside the Editor folder

3. Run Shinai > DoBuild > Win64

4. You don't need to wait for the entire build to finish, just wait for the Compiling Shader Variants to show up once and then press cancel.

Actual results: 

You will see the error 'Recursive serialization is not allowed for threaded serialization' in the console like in the attached video ([^recursive_serialization_bug.mp4])

Expected results: 

The 'Recursive serialization is not allowed for threaded serialization' should not be thrown in the console.