The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b7da1a4e6d4ec2ec10c58a50a90ba14fe7c7a828

commit b7da1a4e6d4ec2ec10c58a50a90ba14fe7c7a828
Author: Manu Cornet <manucornet@chromium.org>
Date: Mon Sep 17 17:11:45 2018

CrOS Shelf: Don't show delayed tooltips after mouseout event

This prevents the behavior whereby the user would mouse over a shelf
item, then mouse out before the tooltip had appeared, and the tooltip
would still unexpectedly appear.

Bug:  883534 
Change-Id: I8ec069d392c08a00003ba380d8aa0ee1a3c7ec8f
Reviewed-on: https://chromium-review.googlesource.com/1226432
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591716}
[modify] https://crrev.com/b7da1a4e6d4ec2ec10c58a50a90ba14fe7c7a828/ash/shelf/shelf_tooltip_manager.cc