Is this an existing issue? A regression? 

CL to fix: https://chromium-review.googlesource.com/c/chromium/src/+/704739

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5780d94a1b2e5e447f8d19a166f2bd017f252eca

commit 5780d94a1b2e5e447f8d19a166f2bd017f252eca
Author: Becca Hughes <beccahughes@chromium.org>
Date: Tue Oct 10 16:30:38 2017

Media Controls: Disable text selection on the overflow menu

Text on the overflow menu should not be selectable.

BUG= 771950 

Change-Id: I2636ae203f0c357172cd39fe64e085410f8cb3a6
Reviewed-on: https://chromium-review.googlesource.com/704739
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#507687}
[modify] https://crrev.com/5780d94a1b2e5e447f8d19a166f2bd017f252eca/third_party/WebKit/Source/modules/media_controls/resources/legacyMediaControls.css