Reland "Clipboard: Add test helper for portable type checks"

This is a reland of b65ee036

This reland updates how URLs are checked on Macs. The trybot which
failed on the original CL has been added to Cq-Include-Trybots.

Original change's description:
> Clipboard: Add test helper for portable type checks
>
> For portable types, reading from the clipboard involves both a check of
> IsFormatAvailable() and ReadAvailableTypes(). This CL adds a helper
> which does both of these checks, simplifying the code and reducing the
> chances that new code will accidentally only check one of these
> methods (see: https://crbug.com/1215137).
>
> For non-portable types, comments have been left to explain why this
> helper is not used.
>
> Bug: 1241712, 1215137
> Change-Id: I25f03a2d4c2559e688fbf26a06893cde4725d673
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3111332


> Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
> Reviewed-by: Darwin Huang <huangdarwin@chromium.org>
> Commit-Queue: Austin Sullivan <asully@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#914517}

Bug: 1241712, 1215137, 1242731
Change-Id: I87c1397449fea42b866ecdd4dbd773771c770e4b
Cq-Include-Trybots: luci.chromium.try:mac-official;luci.chromium.try:win-official
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3123739


Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Auto-Submit: Austin Sullivan <asully@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/main@{#917733}