Allow gaming_seat to use ozone gamepad as back-end

chrome/common/features.gni

Index: chrome/common/features.gni
diff --git a/chrome/common/features.gni b/chrome/common/features.gni
index 6dc3771def343fe47ae2b0eb1101ef0edce35c9a..8c389e43c999ad8ff5c0b8a157546366c6fec895 100644
--- a/chrome/common/features.gni
+++ b/chrome/common/features.gni
@@ -49,6 +49,10 @@ declare_args() {
   enable_one_click_signin =
       is_win || is_mac || (is_linux && !is_chromeos && !is_chromecast)
 
+  # Indicates if Exo should use ozone gamepad. If this is false, exo will use
+  # /device/gamepad as backend.
+  enable_exo_ozone_gamepad = use_ozone && false
+
   # Set to true to bundle all the mash related mojo services into chrome.
   # Specify --mash to chrome to have chrome start the mash environment.
   enable_package_mash_services = is_chromeos