IIRC Yoshiki-san is working on this.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/101b811383bbcdefaa86e864275afbea17d902f8

commit 101b811383bbcdefaa86e864275afbea17d902f8
Author: yoshiki iguchi <yoshiki@chromium.org>
Date: Wed Aug 16 05:55:02 2017

Remove unnecessary operation on opening message center.

This CL removes unnecessary image operation on opening message center. With this CL, opening the message center gets 50-500 times faster.

Bug: b/64544553
Bug:  750587 
Change-Id: I045f1a285fcacb6dafb997ad2fefbfe4ad54791b
Reviewed-on: https://chromium-review.googlesource.com/616520
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Commit-Queue: Yoshiki Iguchi <yoshiki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#494703}
[modify] https://crrev.com/101b811383bbcdefaa86e864275afbea17d902f8/chrome/browser/notifications/arc_application_notifier_source_chromeos.cc

Shall we merge to 61?

Approving merge to M61 Chrome OS.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d2df5354f5998fbecb9c600d73a18a84a3b71c77

commit d2df5354f5998fbecb9c600d73a18a84a3b71c77
Author: yoshiki iguchi <yoshiki@chromium.org>
Date: Fri Aug 18 05:09:02 2017

Remove unnecessary operation on opening message center.

This CL removes unnecessary image operation on opening message center. With this CL, opening the message center gets 50-500 times faster.

TBR=yoshiki@chromium.org

(cherry picked from commit 101b811383bbcdefaa86e864275afbea17d902f8)

Bug: b/64544553
Bug:  750587 
Change-Id: I045f1a285fcacb6dafb997ad2fefbfe4ad54791b
Reviewed-on: https://chromium-review.googlesource.com/616520
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Commit-Queue: Yoshiki Iguchi <yoshiki@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#494703}
Reviewed-on: https://chromium-review.googlesource.com/620429
Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Cr-Commit-Position: refs/branch-heads/3163@{#670}
Cr-Branched-From: ff259bab28b35d242e10186cd63af7ed404fae0d-refs/heads/master@{#488528}
[modify] https://crrev.com/d2df5354f5998fbecb9c600d73a18a84a3b71c77/chrome/browser/notifications/arc_application_notifier_source_chromeos.cc