Created attachment 174432 [details]
Because of rounding issues the rendering in regions when using subpixel layout is not similar to the reference. See the attached test file.
Created attachment 174433 [details]
Reference for test
Works for me on today's nightly (r151543)
As long as the sub-pixel layout code is still in WebKit (even if it's disabled in the Mac port), the bug should still be open.