The tests started failing in https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win10/builds/8300
One CL that stands out on the blamelist is https://codereview.chromium.org/1848263002 which has changed test expectations for some of the failing tests (i.e. quirks-percentage-height-body-expected.txt).
Failing tests:
printing/quirks-percentage-height-body.html
printing/quirks-percentage-height.html
printing/standards-percentage-heights.html
printing/subframes-percentage-height.html
virtual/threaded/printing/quirks-percentage-height-body.html
virtual/threaded/printing/quirks-percentage-height.html
virtual/threaded/printing/standards-percentage-heights.html
virtual/threaded/printing/subframes-percentage-height.html
Comment 1 by lukasza@chromium.org
, Apr 1 2016