Marks media/controls/repaint-on-resize.html as flaky on Mac 10.11

TBR=avayvod@chromium.org, beccahughes@chromium.org

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 789921
Change-Id: Id8433239e4c12bd115330bbaee3e43e3afe5e204
Reviewed-on: https://chromium-review.googlesource.com/926403
Commit-Queue: Maxim Kolosovskiy <kolos@chromium.org>
Reviewed-by: Maxim Kolosovskiy <kolos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537773}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3031,6 +3031,7 @@ crbug.com/781935 fast/mediastream/MediaStreamTrack.html [ Timeout ]
 # Sheriff failures 2017-10-04
 crbug.com/770691 [ Win7 Linux Mac10.11 ] media/controls/lazy-loaded-style.html [ Failure Pass ]
 crbug.com/770691 [ Win7 Linux Mac10.11 ] virtual/new-remote-playback-pipeline/media/controls/lazy-loaded-style.html [ Failure Pass ]
+crbug.com/770691 [ Mac10.11 ] media/controls/repaint-on-resize.html [ Failure Pass ]
 
 crbug.com/807191 fast/media/mq-color-gamut-picture.html [ Pass Failure Timeout ]