Convert some instances of WebUI::DeprecatedMessageCallback to

WebUI::MessageCallback

Part of code health rotation

Split of https://crrev.com/c/3529288, converts instances
in /chrome/browser/ui/webui/offline

Also remove ListValue forward declaration as per presubmit checks

This does not fix all usages of the deprecated interface

This CL was uploaded by git cl split.

R=jianli@chromium.org

Bug: 1243386
Change-Id: Iba587689aa359d9b4c31ec91a0189eabf495230c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3545486
Auto-Submit: Michael Wilson <mjwilson@chromium.org>
Reviewed-by: Jian Li <jianli@chromium.org>
Commit-Queue: Jian Li <jianli@chromium.org>
Cr-Commit-Position: refs/heads/main@{#984634}