according to our other shared icon tooltip code, the font's supposed to be 12px. Is that fine?

https://cs.chromium.org/chromium/src/ui/webui/resources/cr_elements/policy/cr_tooltip_icon.html?q=cr_tooltip_icon&sq=package:chromium&l=17

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9458ef4e2a08e52ee7d017ed155a84e855d07b1e

commit 9458ef4e2a08e52ee7d017ed155a84e855d07b1e
Author: Scott Chen <scottchen@chromium.org>
Date: Wed Nov 29 12:51:57 2017

MD Extensions: use paper-tooltip for extension's source-indicator.

This CL makes the tooltip style more consistent with other UI by using the same
element and styling for the source-indicator on extensions landing page.

Bug:  787222 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ied83dc00237694333f208096042ffd017f76d85d
Reviewed-on: https://chromium-review.googlesource.com/790370
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Scott Chen <scottchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520086}
[modify] https://crrev.com/9458ef4e2a08e52ee7d017ed155a84e855d07b1e/chrome/browser/resources/md_extensions/item.html
[modify] https://crrev.com/9458ef4e2a08e52ee7d017ed155a84e855d07b1e/ui/webui/resources/cr_elements/policy/cr_tooltip_icon.html
[modify] https://crrev.com/9458ef4e2a08e52ee7d017ed155a84e855d07b1e/ui/webui/resources/cr_elements/shared_vars_css.html

Assuming this is fixed now. Please re-open if not.