How to reproduce:
1. Create a new project
2. Create a new gameObject and add the Polygon Collider 2D collider to it
3. Observe Inspector window

Expected result: There is a button next to to the Edit Collider text allowing to edit the collider
Actual result: The button next to to the Edit Collider text is missing meaning the user can't edit the collider

Reproducible with: 2019.3.0a7, 2019.3.0a8
Not reproducible with: 2017.4.29f1, 2018.4.3f1, 2019.1.8f1, 2019.2.0b8, 2019.3.0a6