Steps to reproduce:

1. Open Unity on OSX;
2. Create new project;
3. Import attached 'tree' package;
4. Open 'test' scene;
5. Go to PlayerSettings (Edit -> Project Settings -> Player);
6. Expand 'Other Settings' tab;
7. Click on a '+' sign;
8. Add 'Metal' platform;
9. Drag Metal platform on top of OpenGlCore;
10. Click Apply button;
11. Observe the console.

Actual result:
Error:
'Internal: Possible leak. All textures should be removed from IdMap when destructed using RemoveTexture(TextureID texid).' is shown (see attached gif video).

Expected result:
Error should not be shown when switching graphics API.

Notes:
- Reproducible in OSX 10.11.6;
- Reproducible in 5.5.0b5, 5.4.1p2. 5.4.0f3. 5.3.6p2;
- Not reproducible in the empty new scene; seems to be specific for this project.