Mark media/controls/text-track-menu-pointer-selection.html as slow

Tbr: mlamouri@chromium.org
No-Try: true
Bug: 865262
Change-Id: I8b4e49744783c45c84a80fe1560e4e21133f4d0e
Reviewed-on: https://chromium-review.googlesource.com/1142858Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576361}

third_party/WebKit/LayoutTests/SlowTests

@@ -401,3 +401,5 @@ crbug.com/833215 external/wpt/accelerometer/Accelerometer.https.html [ Slow ]
 crbug.com/861670 [ Linux Mac ] virtual/gpu/fast/canvas/canvas-blending-image-over-gradient.html [ Slow ] 
 
 crbug.com/864887 [ Mac ] fast/scroll-snap/snaps-after-scrollbar-scrolling.html [ Slow ]
+
+crbug.com/865262 [ Mac ] media/controls/text-track-menu-pointer-selection.html [ Slow ]