update_engine: Turn on Chrome Kiosk app by default

This flag is always true in Chorme OS and android's code doesn't compile
this. So the flag can be removed and be turned on by default.

BUG=b:171829801
TEST=cros_workon_make --board reef --test

Change-Id: Ibb7423196f24793adf85ef5bfe7da7b1edef012a
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2528758
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index c5430f9..a6e4b81 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -81,7 +81,6 @@
     "USE_DBUS=${use.dbus}",
     "USE_FEC=0",
     "USE_HWID_OVERRIDE=${use.hwid_override}",
-    "USE_CHROME_KIOSK_APP=${use.chrome_kiosk_app}",
     "USE_SHILL=1",
   ]
   include_dirs = [
@@ -270,6 +269,7 @@
   deps = [
     ":libpayload_consumer",
     ":update_engine-dbus-adaptor",
+    ":update_engine-dbus-kiosk-app-client",
     ":update_metadata-protos",
   ]
 
@@ -281,10 +281,6 @@
     sources += [ "cros/chrome_browser_proxy_resolver.cc" ]
   }
 
-  if (use.chrome_kiosk_app) {
-    deps += [ ":update_engine-dbus-kiosk-app-client" ]
-  }
-
   if (use.dlc) {
     sources += [
       "cros/dlcservice_chromeos.cc",