Fix LayoutStateObserver related NPE in ChromeMessageQueueMediator

The issue is that sometimes
ChromeMessageQueueMediator#setLayoutStateProvider is called after
ChromeMessageQueueMediator#destroy, followed immediately by a
notification. By this time ChromeMessageQueueMediator state is destroyed
causing NPE.

This CL adds CallbackController to ChromeMessageQueueMediator to prevent
a call to #setLayoutStateProvider() after #destroy().

BUG=1199059,1216002
R=lazzzis@chromium.org

Change-Id: Ibefb124f861ad8d3476f9b0f943528b68a5ed77d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2951646
Reviewed-by: Lijin Shen <lazzzis@google.com>
Commit-Queue: Pavel Yatsuk <pavely@chromium.org>
Cr-Commit-Position: refs/heads/master@{#891279}