Steps to reproduce:
1. Open "LightingDataLoading" project
2. Open "Start" scene
3. "Build and run" this project
4. Push button "Load scene WITH lightingData"
- After several seconds window freezes and later it stops responding for about 10-15 seconds.
note: If you just run built exe, it loads way faster (on my computer it took about 3 seconds).

Expected: "Build and run" build scene loading time doesn't differ from executed build.
Actual: "Build and run" build scene loading takes way more time, freezes and stops responding game window.

Tested on: Windows 10 Pro,AMD FX(TM)-8350 Eight-Core Processor @ 4.00 GHz,8 GB, NVIDIA GeForce GTX 750

Reproduced with: Unity 5.4.0b15; 5.4.0b16; 5.3.4f1; 5.3.2p1