Remove paint/masks/fieldset-mask.html from SlowTests

TBR=fs@opera.com
BUG=529345

Change-Id: If867ae6936ccfadfd99e4cff4ea209c686f99382
Reviewed-on: https://chromium-review.googlesource.com/1249395
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594942}
1 file changed