rgbkbd: Add SetZoneColor stub API

BUG=b:259589687
TEST=local

Change-Id: Ic23e7d167ed082fe806251cc00bbafa55fecd328
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/4053891
Tested-by: Anton Swifton <swifton@google.com>
Reviewed-by: David Padlipsky <dpad@google.com>
Commit-Queue: Anton Swifton <swifton@google.com>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
NOKEYCHECK=True
GitOrigin-RevId: aacd4ee2165a0e92a95e6239b8c45c1c712b468e
diff --git a/dbus/rgbkbd/dbus-constants.h b/dbus/rgbkbd/dbus-constants.h
index fe67abe..bc00332 100644
--- a/dbus/rgbkbd/dbus-constants.h
+++ b/dbus/rgbkbd/dbus-constants.h
@@ -14,6 +14,7 @@
 const char kGetRgbKeyboardCapabilities[] = "GetRgbKeyboardCapabilities";
 const char kSetCapsLockState[] = "SetCapsLockState";
 const char kSetStaticBackgroundColor[] = "SetStaticBackgroundColor";
+const char kSetZoneColor[] = "SetZoneColor";
 const char kSetRainbowMode[] = "SetRainbowMode";
 const char kSetTestingMode[] = "SetTestingMode";
 const char kSetAnimationMode[] = "SetAnimationMode";