does this only happen on Mac?

I only tried Mac Canary, because Linux does not have auto-update anyway. Have not figured out how to try it on ChromeOS, and don't have a win device either.

i'm fairly sure this is a Mac-specific bug because the Mac-specific version updater doesn't support incremental updates (i.e. doesn't send a progress other than 0).

https://cs.chromium.org/chromium/src/chrome/browser/ui/webui/help/version_updater_mac.mm?sq=package:chromium&dr=CSs&l=239

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0b695038aa4397ef763fc51b80fbdb0202026b6e

commit 0b695038aa4397ef763fc51b80fbdb0202026b6e
Author: dbeam <dbeam@chromium.org>
Date: Wed Nov 09 23:39:25 2016

MD Settings: ignore 0% updates on help/about page

R=dpapad@chromium.org
BUG= 663507 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2476353007
Cr-Commit-Position: refs/heads/master@{#431080}

[modify] https://crrev.com/0b695038aa4397ef763fc51b80fbdb0202026b6e/chrome/app/settings_chromium_strings.grdp
[modify] https://crrev.com/0b695038aa4397ef763fc51b80fbdb0202026b6e/chrome/app/settings_google_chrome_strings.grdp
[modify] https://crrev.com/0b695038aa4397ef763fc51b80fbdb0202026b6e/chrome/app/settings_strings.grdp
[modify] https://crrev.com/0b695038aa4397ef763fc51b80fbdb0202026b6e/chrome/browser/resources/settings/about_page/about_page.js
[modify] https://crrev.com/0b695038aa4397ef763fc51b80fbdb0202026b6e/chrome/browser/ui/webui/settings/md_settings_localized_strings_provider.cc
[modify] https://crrev.com/0b695038aa4397ef763fc51b80fbdb0202026b6e/chrome/test/data/webui/settings/about_page_tests.js

this should show only 1% or higher for when Chrome is updating (except for the subtle case of also changing the target platform on ChromeOS, but that doesn't really matter to me as much because ChromeOS actually has useful percent while updating)