All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=649975

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyfQsSE1N0b3BwYWdlQWxlcnRQYXJlbnQiT0Nocm9taXVtUGVyZi9jaHJvbWl1bS1yZWwtd2luNy1ncHUtYXRpL3Ntb290aG5lc3MudG9wXzI1X3Ntb290aC9mcmFtZV90aW1lcy9yZWYMCxINU3RvcHBhZ2VBbGVydBjPxxkM,agxzfmNocm9tZXBlcmZyigELEhNTdG9wcGFnZUFsZXJ0UGFyZW50IlxDaHJvbWl1bVBlcmYvY2hyb21pdW0tcmVsLXdpbjctZ3B1LWF0aS9zbW9vdGhuZXNzLnRvcF8yNV9zbW9vdGgvbWVhbl9pbnB1dF9ldmVudF9sYXRlbmN5L3JlZgwLEg1TdG9wcGFnZUFsZXJ0GM_HGQw,agxzfmNocm9tZXBlcmZygwELEhNTdG9wcGFnZUFsZXJ0UGFyZW50IlVDaHJvbWl1bVBlcmYvY2hyb21pdW0tcmVsLXdpbjctZ3B1LWF0aS9zbW9vdGhuZXNzLnRvcF8yNV9zbW9vdGgvcGVyY2VudGFnZV9zbW9vdGgvcmVmDAsSDVN0b3BwYWdlQWxlcnQYz8cZDA


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

chromium-rel-win7-gpu-ati

This happened around Sept 15.

Screenshot: https://screenshot.googleplex.com/j2oM59RkY5h

+aiolos: Is the "ref" series the reference build? Did something happen with reference builds around sept 15?

ref is reference build, and this is most likely  crbug.com/650762 

"smoothnes.top_25_smooth failing on almost all windows bots on chromium.perf"

Thanks!