Performance dashboard identified a 14.4% regression in cheets_PerfBootServer/boot_progress_pms_data_scan_start on cros-veyron_minnie at revision range 29150000898200001:29170000898300000. Graph: https://chromeperf.appspot.com/report?masters=ARC&bots=cros-veyron_minnie&tests=cheets_PerfBootServer%2Fboot_progress_pms_data_scan_start&checked=boot_progress_pms_data_scan_start%2Cboot_progress_pms_data_scan_start_ref%2Cref&rev=29170000898300000

Same happened on elm and kevin (but not as significant as minnie)
https://chromeperf.appspot.com/report?sid=fc2d725c60a04258bd81b098341faa8b780c64d9926c58734b8d9ca96bc724af&rev=29170000898300000

Trying bisection.