arc: Provide API to control Play Store state from autotests

chrome/browser/chromeos/arc/arc_util.h

Index: chrome/browser/chromeos/arc/arc_util.h
diff --git a/chrome/browser/chromeos/arc/arc_util.h b/chrome/browser/chromeos/arc/arc_util.h
index 7765832e9abad9327bef3b6adbac810e0718fc6c..aee7a902d47ada363f928e17acecc1d01a0456a3 100644
--- a/chrome/browser/chromeos/arc/arc_util.h
+++ b/chrome/browser/chromeos/arc/arc_util.h
@@ -71,8 +71,9 @@ bool IsArcPlayStoreEnabledPreferenceManagedForProfile(const Profile* profile);
 // the given |profile|.
 // TODO(hidehiko): De-couple the concept to enable ARC system and opt-in
 // to use Google Play Store. Note that there is a plan to use ARC without
-// Google Play Store, then ARC can run without opt-in.
-void SetArcPlayStoreEnabledForProfile(Profile* profile, bool enabled);
+// Google Play Store, then ARC can run without opt-in. Returns false in case
+// enabled state of the Play Store cannot be changed.
+bool SetArcPlayStoreEnabledForProfile(Profile* profile, bool enabled);
 
 // Returns whether all ARC related OptIn preferences (i.e.
 // ArcBackupRestoreEnabled and ArcLocationServiceEnabled) are managed.