Currently, chromeperf is using window_size=100 for anomaly detection for ChromeOS_Graphics/*/Failures*, which makes some of our test failures are not detected. Let's lower this to let it more error sensitive.

https://chromeperf.appspot.com/report?sid=671a618c3429a50f6b997556bd012427f5bc577209cfec19816ca0d23628d379

@sullivan
Test owner (see http://go/perf-test-owners): chromeos-gfx-alerts@google.com
Buildbot master name:
Test suite names: ChromeOS_Graphics
Restrict to these specific traces (if any):
Email address and/or URL of sheriff rotation: chromeos-gfx-alerts@google.com
Receive individual email alerts immediately or as a daily summary? immediately 
Should these alerts be Google-internal? As before

Could you change the config for
ChromeOS_Graphics/*/Failures* to the following setting? 
{
  "max_window_size": 20, 
  "min_segment_size": 3
}