s/\bArc\b/ARC/g for ARC related code.

chrome/browser/chromeos/arc/arc_optin_uma.h

Index: chrome/browser/chromeos/arc/arc_optin_uma.h
diff --git a/chrome/browser/chromeos/arc/arc_optin_uma.h b/chrome/browser/chromeos/arc/arc_optin_uma.h
index 4e4f534ed176f708a65ab57527624407572d8949..d73764406e6c8f2a51aa0a36100031c1a5433ec2 100644
--- a/chrome/browser/chromeos/arc/arc_optin_uma.h
+++ b/chrome/browser/chromeos/arc/arc_optin_uma.h
@@ -16,11 +16,11 @@ namespace arc {
 // These enums are used to define the buckets for an enumerated UMA histogram
 // and need to be synced with histograms.xml
 enum class OptInActionType : int {
-  OPTED_OUT = 0,               // Arc was opted out by user.
-  OPTED_IN = 1,                // Arc was opted in by user.
-  NOTIFICATION_ACCEPTED = 2,   // Arc OptIn notification was accepted.
-  NOTIFICATION_DECLINED = 3,   // Arc OptIn notification was declined.
-  NOTIFICATION_TIMED_OUT = 4,  // Arc OptIn notification was timed out.
+  OPTED_OUT = 0,               // ARC was opted out by user.
+  OPTED_IN = 1,                // ARC was opted in by user.
+  NOTIFICATION_ACCEPTED = 2,   // ARC OptIn notification was accepted.
+  NOTIFICATION_DECLINED = 3,   // ARC OptIn notification was declined.
+  NOTIFICATION_TIMED_OUT = 4,  // ARC OptIn notification was timed out.
   RETRY = 5,                   // User asked to retry OptIn.
   SIZE,                        // The size of this enum; keep last.
 };