Block corners are miss-aliased

[griffpatch]

Expected Behavior

Corners of scratch blocks should be rounded nicely.

Actual Behavior

Corners are rendered heavier than expected such that they do not appear as nicely rounded as they should:

Steps to Reproduce

Open in Chrome and look at the blocks panel.

Operating System and Browser

Chrome Latest on Windows PC

[thisandagain]

/cc @carljbowman @ericrosenbaum @paulkaplan We've talked about this a bit in the past, but it's good to have something filed.