Reproduction steps:
1. Open the project
2. Hit Ctrl+Shift+B
3. Uncheck Autoconnect Profiler and Development Build
4. Hit Build and Run
5. As soon as you will get into the game after splash screen start moving your mouse and walk(W/A/S/D)
6. Close the game and go back to Unity
7. Check Autoconnect Profiler and Development Build
8. Hit Build and Run
9. As soon as you will get into the game after splash screen move mouse and walk
10. Notice the unaccounted processor time in the Profiler

Note: If you build this project 2 times in a row with Development Build and Autoconnect Profiler enabled bug disappears
Note: If you build this project 2 times in a row with Development Build and Autoconnect Profiler disabled bug disappears

Alternative reproduction steps:
1. Open the project
2. Play the only scene
3. Notice the unaccounted time in the profiler
Note: Alternative steps are not consistent and unaccounted time period is very small.

Note: Profiler on 5.5.0b4 shows "Unaccounted time between: WaitForTargetFPS and Loading.UpdateWebStream".

Reproduced on: 5.5.0b4, 5.4.1p1, 5.4.0p1
Not reproducable on: 5.3.6p5