3200 15-15-15 should be Samsung just because there are no Hynix or Micron IC in mass sales at so tight timings.
G.Skill is not sharing what IC they are using since beginning of this year when they started to use Hynix in Trident Z RGB and Ripjaws V 3000/3200 at more relaxed timings ( read CL15-16-16, 16-16-16, 16-18-18 ). However I'm almost sure that 3200 CL15-15-15 or any higher frequency memory kits are still based on Samsung IC because Hynix/Micron simply can't work at these settings.