All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=883748

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=e30f31129c61751045f09a02ace83edaa18d3e313c07deae729a23188eedf6ac


Bot(s) for this bug's original alert(s):

Win 7 Nvidia GPU Perf

rendering.desktop - Benchmark documentation link:
  https://bit.ly/rendering-benchmarks

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/124b63fb640000

📍 Couldn't reproduce a difference.
https://pinpoint-dot-chromeperf.appspot.com/job/124b63fb640000

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/106ab8e3640000

📍 Found significant differences after each of 3 commits.
https://pinpoint-dot-chromeperf.appspot.com/job/106ab8e3640000

Version 7.0.276 by v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com
https://chromium.googlesource.com/v8/v8/+/6e2adae6f7f8e891cfd01f3280482b20590427a6
0.3101 → 0.4427 (+0.1325)

[LayoutNG] Split offset from NGPhysicalFragment by eae@chromium.org
https://chromium.googlesource.com/chromium/src/+/6319b177ec0c178be86278b440260c095830ac0c
0.4456 → 0.4635 (+0.01789)

Roll clang 338452:340925 by hans@chromium.org
https://chromium.googlesource.com/chromium/src/+/d54494cbad8d5ff0a8cd74024902c8bd86258ae4
0.46 → 0.4241 (-0.03588)

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

Benchmark documentation link:
  https://bit.ly/rendering-benchmarks

Not sure why this got assigned to me..

It looks like the benchmark recovered in the 590980 - 591072 range (which doesn't include anything clang related).

From #5 it also looks like the performance improved slightly in the Clang roll, whereas the bug title talks about a "51.1% regression".