Refactor chrome theme files (.grd)

This change is a no-op, it just improves code readability.

- Use <if>, <then>, <else>
- Use positive booleans (http://go/tott/387)

Bug: 1336611
Change-Id: I3b46d553185e0d7a4dad4893d39ed174292b8ca6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3889981


Reviewed-by: Colin Blundell <blundell@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Auto-Submit: Thiago Perrotta <tperrotta@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1045778}