I think that a subtle change to how the blend-mode works caused this. At one point, I believe that if there was no SkShader on the paint, then the blend-mode was ignored (it just drew using the vertex colors). Now, the specification is consistent with the rest of Skia: The blend that happens between the vertex colors and the paint ALWAYS happens. The SRC of that blend is the SkShader, if present, otherwise it's the opaque paint color. To get the old behavior (just draw with the vertex colors), you can just switch the blend mode to kDst:
https://fiddle.skia.org/c/9b7036bc50b7ee261db65ced80f38bce