arc: Enable silent PlayStore Sign-In.

chromeos/chromeos_switches.cc

Index: chromeos/chromeos_switches.cc
diff --git a/chromeos/chromeos_switches.cc b/chromeos/chromeos_switches.cc
index faf101997a58ec16b26ce19706f545be1a3cc0cc..8378fe5b51e60707c6a10cb35bf18ccdc4430a52 100644
--- a/chromeos/chromeos_switches.cc
+++ b/chromeos/chromeos_switches.cc
@@ -61,6 +61,10 @@ const char kAppOemManifestFile[] = "app-mode-oem-manifest";
 // Signals the availability of the ARC instance on this device.
 const char kArcAvailable[] = "arc-available";
 
+// Specifies ARC authorization endpoint to enable automatic sign-in in OptIn
+// flow.
+const char kArcUseAuthEndpoint[] = "arc-use-auth-endpoint";
+
 // Screenshot testing: specifies the directoru where artifacts will be stored.
 const char kArtifactsDir[] = "artifacts-dir";