Fix snackbar transparency when other bottom controls are showing

When scrolling down the browser controls with the snackbar showing, there's an odd issue where the snackbar gets cut off and shows as partially transparent. This has been fixed / mitigated by showing a dummy transparent view covering the bottom inset when drawing edge-to-edge and showing the bottom chin.

A change to the visibility model to better integrate with other browser controls started accidentally hiding the dummy Android view early, once the chin had scrolled off, but before the rest of browser controls had scrolled off - this is why the transparency cutoff bug was happening again, but seemed to align with the bottom toolbar, rather than the bottom chin. This is also why the bug didn't reproduce if the bottom chin was the only browser controls component present.

This fix ensures the Android view is shown anytime the bottom chin can show, even if it is currently scrolled off.

(cherry picked from commit 6d8b2508)

Bug: 373969376
Change-Id: I6f7d90654fa05572ebe3b2feb2fb10be937b4fa7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5943330


Commit-Queue: Charles Hager <clhager@google.com>
Reviewed-by: Wenyu Fu <wenyufu@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1371589}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5954425
Cr-Commit-Position: refs/branch-heads/6778@{#596}
Cr-Branched-From: b21671ca-refs/heads/main@{#1368529}