Operating system: windows 10
Graphics card: GEForce RTX 2080 super
Blender Version 2.9
Broken: (example: 2.80, edbf15d3c044, master, 2018-11-28, as found on the splash screen)
Worked: (newest version of Blender that worked as expected)
Short description of error
Gradient layers not working properly with Grease Pencil if you open the example file https://cloud.blender.org/p/gallery/5c30cf5f637c8d7750c8aa6c you will see that applying the mask to the gradient layer does not work as in the preview from the old version of blender, the layer is not "multiplying" to give a sense of shadow on the lower layers of Grease pencil it just looks like a dirty overlay, also radial gradients do not work or are not visible.
Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).