Reproduction steps:

1. Open "IL2CPPMarshalRepro.zip" project
2. Open "Scene" scene
3. Enter Play Mode
4. See Console window output (Everything has a value, no exception errors)
5. Build and Run for WebGL
6. Open your browsers Console window ("Ctrl" + "Shift" + "J" for Chrome)
7. See error "Failure: Type 'GameObjectData' cannot be marshaled as an unmanaged structure; no meaningful size or offset can be computed."

Fixed in: 2019.1.0a8, 2018.3.0b9, 2018.2.16f1, 2017.4.15f1

Expected Result: Console output is the same as in Editor / No exception errors occur
Actual Result: Errors appear in the Browser Console

Reproduced with: 2019.1.0a2, 2018.3.0b3, 2018.2.9f1, 2018.1.9f2, 2017.4.11f1