Steps to reproduce the issue:
1. Download and open the attached project (dropbox link is provided by the user).
2. Switch platform to iOS.
3. In the "Player Settings" select OpenGLES2 or OpenGLES3 as Graphics API.
4. Build the project.
5. Connect iOS device, build and run the game through xCode.
6. Notice that the image effects work as expected.
7. In the "Player Settings" select Metal as Graphics API.
8. Repeat 4 and 5 steps.

Actual result:
Image effects are broken.

Expected result:
Image effects should work as expected.

Note:
Image effects work in the Editor, OpenGLES2 and OpenGLES3, but not Metal and DX11.

Reproduced with:
5.4.0f3, 5.4.0p4, 5.5.0b1.

Cannot reproduce with:
5.1.5f1, 5.2.5f1, 5.3.6f1 because of this error message:
Assets/Standard Assets/Image Effects (Pro Only)/DepthOfFieldScatter.js(93,82): BCE0019: 'IndirectArguments' is not a member of 'UnityEngine.ComputeBufferType'.