How to reproduce:
1. Open the user-submitted project(ShaderKeywords)
2. Build the project as a Development Build and open it
3. Back in the Editor open the Frame Debugger window
4. Enable the Frame Debugger for the Editor, find Draw Mesh Cube event and check its keywords
5. Attach the Frame Debugger to the build, find the 'Draw Mesh' event for the Cube and check its keywords

Expected result: _METALLICGLOSSMAP keyword is among the keyword list
Actual result: _METALLICGLOSSMAP is missing from the keyword list

Reproducible with: 2017.2.3p2, 2018.4.9f1, 2018.1.9f2, 2018.2.6f1, 2018.3.0a10
Not reproducible with: 2017.1.5f1

Notes:
Additional keywords are still listed if using Debug.LogError to list the keywords in the player
Different versions of Unity may produce different keyword results when debugging the build