Revert "[client-hints] Calculate correct values for viewport width and height on"

This reverts commit f3f90d94.

Reason for revert: https://crbug.com/1247549, crashing in getting the viewport size.

Original change's description:
> [client-hints] Calculate correct values for viewport width and height on
> navigation requests.
>
> Currently on navigation requests, the viewport-width and sec-ch-viewport-height client hints are calculated using the display's dimensions. This CL updates the two clients to use the visible viewport size, which provides more accurate information.
>
> The CL also handles prefetch requests. In a prefetch request, the frame_tree_node is null, so we need a separate mechanism to track the viewport size. This is done by a new ClientHintsWebContentsObserver.
>
> Reimplementation of the reverted CL: https://chromium-review.googlesource.com/c/chromium/src/+/2494876
>
> Bug: 825892
> Change-Id: Id3117cfa505c33d59eb7dbb8cc8b485dd567f792
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3108448


> Reviewed-by: Avi Drissman <avi@chromium.org>
> Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
> Commit-Queue: Max Curran <curranmax@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#918864}

Bug: 825892, 1247549
Change-Id: I497deb56a45aaf78c19d07d17b31bac3e4d7d5bb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3148038


Auto-Submit: Avi Drissman <avi@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Owners-Override: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#919271}