ChromeOS: Disable ARC when incompatible filesystem is detected.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index a47c1be56a70863342b6cba6e4f65afc1daa5ac8..f6eb0896507e0a4d8480861adc447797e312f4e2 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -47,6 +47,10 @@ const char kArcSetNotificationsEnabledDeferred[] =
     "arc.set_notifications_enabled_deferred";
 // A preference that indicates status of Android sign-in.
 const char kArcSignedIn[] = "arc.signedin";
+// A preference that indicates an ARC comaptible filesystem was chosen for
+// the user directory (i.e., the user finished required migration.)
+extern const char kArcCompatibleFilesystemChosen[] =
+    "arc.compatible_filesystem.chosen";
 #endif
 
 // A bool pref that keeps whether the child status for this profile was already