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

[reveman, 2017/06/06 21:58:55]

so how to we enable this in a build now?

[jkwang, 2017/06/07 18:03:18]

What I was thinking is to change this to use_ozone && is_chromeos later.

[reveman, 2017/06/07 20:29:45]

Why not make it so we can enable this using a gn flag instead of having to land
another patch?

[jkwang, 2017/06/07 22:01:45]

Sounds good. How should I do that?

[reveman, 2017/06/08 00:21:43]

I think we should just make it "enable_exo_ozone_gamepad = use_ozone" as why
land this if we're not turning it on somewhere? alternative is
"enable_exo_ozone_gamepad = false" and then require specific boards to turn it
on but I don't see the reason why we'd do that as we want to turn this on for
all boards

+
   # 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