Mark a test as slow.

BUG=719298
TEST=none

Change-Id: I037b7ed1012ee5da35c9d6b654bea76affd9bc79
Reviewed-on: https://chromium-review.googlesource.com/519922
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Commit-Queue: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#476037}

diff --git a/third_party/WebKit/LayoutTests/SlowTests b/third_party/WebKit/LayoutTests/SlowTests
index 88871bfa..52d36d2 100644
--- a/third_party/WebKit/LayoutTests/SlowTests
+++ b/third_party/WebKit/LayoutTests/SlowTests

@@ -386,3 +386,5 @@
 crbug.com/722825 media/controls/video-enter-exit-fullscreen-without-hovering-doesnt-show-controls.html [ Slow ]
 crbug.com/722825 virtual/new-remote-playback-pipeline/media/controls/video-enter-exit-fullscreen-while-hovering-shows-controls.html [ Slow ]
 crbug.com/722825 virtual/new-remote-playback-pipeline/media/controls/video-enter-exit-fullscreen-without-hovering-doesnt-show-controls.html [ Slow ]
+
+crbug.com/719298 fast/dnd/dropEffect-for-effectAllowed.html [ Slow ]