[Chromecast] Require chromecast OWNERS to be aware of locale changes.

chromecast/app/BUILD.gn

Index: chromecast/app/BUILD.gn
diff --git a/chromecast/app/BUILD.gn b/chromecast/app/BUILD.gn
index edf362369acd4cb2dbbac9addf4192aed7750b20..c96064b8348eb8144ca2011bc744faf8d3c61790 100644
--- a/chromecast/app/BUILD.gn
+++ b/chromecast/app/BUILD.gn
@@ -112,4 +112,30 @@ grit("chromecast_settings") {
   foreach(locale, locales_with_fake_bidi) {
     outputs += [ "chromecast_settings_${locale}.pak" ]
   }
+
+  deps = [
+    ":verify_cast_locales",
+  ]
+}
+
+# This target ensures that Chromecast developers are notified when locales
+# change. If this target is breaking the build, the CAST_LOCALES list in
+# //chromecast/app/verify_cast_locales.py must be updated to match
+# |locales_with_fake_bidi|. Please see that file for more details. This action
+# will be run on fresh builds, and whenever |locales_with_fake_bidi| is updated.
+action("verify_cast_locales") {
+  script = "//chromecast/app/verify_cast_locales.py"
+
+  # This file will be stamped on success, preventing an unnecessary rebuild.
+  stamp_file = "$target_gen_dir/cast_locales_verified"
+  args = [
+    "-s",
+    rebase_path(stamp_file, "$root_out_dir"),
+  ]
+
+  args += locales_with_fake_bidi
+
+  outputs = [
+    stamp_file,
+  ]
 }