Disable flaky test font-display.html

Seems to have been flaking for the past several days.

TBR=kojii

Bug: 816026
Change-Id: I335b2c4d49a172a7ae092e8163adf2f6c9cd5f2d
Reviewed-on: https://chromium-review.googlesource.com/936984Reviewed-by: Timothy Loh <timloh@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Timothy Loh <timloh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539066}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3329,6 +3329,9 @@ crbug.com/814907 http/tests/credentialmanager/credentialscontainer-create-from-n
 crbug.com/814953 fast/replaced/no-focus-ring-iframe.html [ Failure Pass ]
 crbug.com/814964 virtual/gpu-rasterization/images/color-profile-border-radius.html [ Failure Pass ]
 
+# Sheriff failures 2018-02-26
+crbug.com/816026 external/wpt/css/css-fonts/font-display/font-display.html [ Failure Pass ]
+
 # MSAN
 crbug.com/813547 [ Linux ] webaudio/BiquadFilter/tail-time-lowpass.html [ Pass Failure ]