Reland "Reland "[Page Zoom] Add unit tests for PageZoomPreference""

This is a reland of commit aad044411044dc3c2b38e1eb871d28aa159fecf2

Original change's description:
> Reland "[Page Zoom] Add unit tests for PageZoomPreference"
>
> This is a reland of commit 847990a16bac77113e321014eebbc528a62ff89d
>
> Original change's description:
> > [Page Zoom] Add unit tests for PageZoomPreference
> >
> > This CL has no functional changes and simply adds tests to increase
> > the code coverage of the PageZoomPreference class.
> >
> > AX-Relnotes: N/A
> > Bug: 1459631, b/265491863
> > Change-Id: I549197322db4d2374e9ee0e580537423e9e9105c
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4893008
> > Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
> > Commit-Queue: Mark Schillaci <mschillaci@google.com>
> > Cr-Commit-Position: refs/heads/main@{#1201818}
>
> Bug: 1459631, b/265491863
> Fixed: 1487148
> Change-Id: Ief9076123f98a3e6c5ae6188a146cb478123beea
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4896273
> Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
> Commit-Queue: Mark Schillaci <mschillaci@google.com>
> Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
> Cr-Commit-Position: refs/heads/main@{#1202102}

Bug: 1459631, b/265491863
Fixed: 1487148
Change-Id: I1c358e52f09477f9298bb00044bce02983eacea1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4900250
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Akihiro Ota <akihiroota@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Mark Schillaci <mschillaci@google.com>
Cr-Commit-Position: refs/heads/main@{#1203247}