Add a code-comment listing all duplicate DEPS-parsing codebases

After the DEPS schema changed in https://crrev.com/c/7007552, there's
been a few codebases that needed similar updating.

Needeless to say, it'd be best if the parsing wasn't duplicated in so
many places. But it's unlikely anyone has the time or motivation to
de-dupe things. So this merely at least tries to document all the
duplicated codebases in the DEPS schema source of truth.

Hopefully this provides some value if/when the schema changes again.

Bug: 448699364
Change-Id: I3f354a2216901c360aea3d4785076f155001de12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/7736646
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Ben Pastene <bpastene@chromium.org>

gclient_eval.py

@@ -120,6 +120,11 @@ def _IsNumericConstant(node):
         and not isinstance(node.value, bool)
 
 # See https://github.com/keleshev/schema for docs how to configure schema.
+# NOTE: If you change this schema, you may need to update other sites that
+# implement their own DEPS-parsing. These include:
+# - http://shortn/_kyy6neydiv
+# - https://skia.googlesource.com/buildbot/+/main/go/depot_tools/deps_parser/
+# - https://chromium.googlesource.com/chromium/tools/build/+/main/recipes/recipe_modules/v8_auto_roller/
 _GCLIENT_DEPS_SCHEMA = _NodeDictSchema({
     schema.Optional(str):
     schema.Or(