Add GN arg "enable_src_internal" and GN global "is_internal_chrome_branded"

Rather than have to maintain a separate non-internal checkout, it's more
convenient to be able to just set a GN arg to disable the internal bits.

This updates most spots that used "is_chrome_branded" as a proxy for
"checkout_src_internal".

Bug: 452971335
Change-Id: Icf33c5afddce68f82e31d3f3cc521e9340a8207f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7080502
Reviewed-by: Peter Wen <[email protected]>
Commit-Queue: Andrew Grieve <[email protected]>
Owners-Override: Andrew Grieve <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1536021}
NOKEYCHECK=True
GitOrigin-RevId: 28bcf1e997b12cbb41217a2d17fcd6d3694261a9
2 files changed