All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=886722

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=e6d533f76a595fab70ca97995a5dbde4e9d3a4313d1b420bb2c215af07b0ba32


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

Win 7 Nvidia GPU Perf

system_health.memory_desktop - Benchmark documentation link:
  https://bit.ly/system-health-benchmarks

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/17182fff640000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/17182fff640000

[Windows 7] Use OS drop shadow for bubble dialogs when Aero mode disabled by alancutter@chromium.org
https://chromium.googlesource.com/chromium/src/+/e86f0201184fcd9c399307e3c96ed4a15f9f8a15
1.955e+07 → 2.082e+07 (+1.273e+06)

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

Benchmark documentation link:
  https://bit.ly/system-health-benchmarks

This makes sense, it's now rendering dialogs in a new native OS window buffer instead of inside the existing one. This allows them to be drawn outside of the main window instead of being clipped.