Mark calendar-picker test flaky on Mac

TBR=ccameron@chromium.org

Bug: 1048149
Change-Id: Ia43d3612f17d99065b5f373f94fe7b5a075b0ec4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2041602Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738977}

third_party/blink/web_tests/TestExpectations

@@ -6628,6 +6628,7 @@ crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/cale
 crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/calendar-picker/date-picker-choose-default-value-after-set-value.html [ Pass Crash ]
 crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/calendar-picker/date-picker-events.html [ Pass Crash ]
 crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/calendar-picker/month-picker-appearance-step.html [ Pass Crash ]
+crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/calendar-picker/month-picker-appearance.html [ Pass Crash ]
 crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/calendar-picker/month-picker-choose-default-value-after-set-value.html [ Pass Crash ]
 crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/calendar-picker/month-picker-key-operations.html [ Pass Crash ]
 crbug.com/1048149 [ Mac ] virtual/form-controls-refresh-disabled/fast/forms/calendar-picker/month-picker-mouse-operations.html [ Pass Crash ]