I was comparing https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Ftryserver.chromium.mac%2Fmac_chromium_rel_ng%2F345353%2F%2B%2Frecipes%2Fsteps%2Fwebkit_tests__with_patch_%2F0%2Fstdout to https://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_ng/builds/345353/steps/webkit_tests%20%28with%20patch%29/logs/stdio today, as the test was still running. You can probably reproduce this with any other live webkit_tests log.

The old-style log updates with a new chunk of text every 1-2 seconds. The logdog log will often lag behind much more, easily 10-20 seconds. That's pretty unfortunate.