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This uses various Windows APIs to try to glean information about the
current layout. Unfortunately, there appears to be no way to get some of
the needed information in a clean fashion through these APIs, so the
implementation uses various guesses and hacks to try to infer it. In the
future, I'd like to look into reading the layout directly from the
layout files, which contain mapping tables that provide all of the
needed information in a known format.

This currently runs in the network process. That means it can't monitor
active window changes and thus never sends an updated layout after the
initial connection. A follow up CL will run the monitor in the desktop
process and communicate the result back via IPC.

Bug: 1026029
Change-Id: Iaba9c0bb0ef2c60fac249a9af392f9434b9c5f93
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1918356
Commit-Queue: Erik Jensen <rkjnsn@chromium.org>
Reviewed-by: Yuwei Huang <yuweih@chromium.org>
Reviewed-by: Gary Kacmarcik <garykac@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720819}