Issue 861711  has been merged into this issue.

Spec: 
https://docs.google.com/presentation/d/1EO7TOpIMJ7QHjaTVw9St-q6naKwtXX2TwzMirG5EsKY/edit#slide=id.g36e7d8d795_33_174

bsep: Sending to you since you're working in this area.

How's this going for branch?

It's in the CQ: https://chromium-review.googlesource.com/c/chromium/src/+/1142614

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7db537ee5e8a1a61342e333194c574ce834aac51

commit 7db537ee5e8a1a61342e333194c574ce834aac51
Author: Bret Sepulveda <bsep@chromium.org>
Date: Thu Jul 19 22:17:47 2018

Add padding between the alert indicator and close button on tabs.

The new padding is per the spec. The padding disappears any time the
close button does. The padding is increased in touch-optimized mode.
There should be no change to pre-Refresh behavior.

This patch also increases the width at which close buttons disappear in
touchable mode, to account for the increased size of all elements.

Bug:  862320 
Change-Id: I75b607d80f0325b8d329213848a11540fdf845b5
Reviewed-on: https://chromium-review.googlesource.com/1142614
Commit-Queue: Bret Sepulveda <bsep@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576660}
[modify] https://crrev.com/7db537ee5e8a1a61342e333194c574ce834aac51/chrome/browser/ui/views/tabs/tab.cc
[modify] https://crrev.com/7db537ee5e8a1a61342e333194c574ce834aac51/chrome/browser/ui/views/tabs/tab.h
[modify] https://crrev.com/7db537ee5e8a1a61342e333194c574ce834aac51/chrome/browser/ui/views/tabs/tab_unittest.cc