drawer heading is removed by accident here:
https://chromium-review.googlesource.com/c/chromium/src/+/679275/13/chrome/browser/resources/md_extensions/manager.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2de3de0b1eb0f4be3cabda7dfb5edee2f42eda9a

commit 2de3de0b1eb0f4be3cabda7dfb5edee2f42eda9a
Author: dpapad <dpapad@chromium.org>
Date: Thu Sep 28 21:50:18 2017

MD Extensions: Restore drawer's title.

This was accidentally removed in a previous CL.

Bug:  769571 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I659501f2b184a475b3beea054283d260a73ca4aa
Reviewed-on: https://chromium-review.googlesource.com/689862
Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505173}
[modify] https://crrev.com/2de3de0b1eb0f4be3cabda7dfb5edee2f42eda9a/chrome/browser/resources/md_extensions/manager.html