handoff: Fix the origin so that it correctly reflects the sender.

components/handoff/handoff_utility.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/handoff/handoff_utility.h"
 
 namespace handoff {
 
 NSString* const kChromeHandoffActivityType = @"com.google.chrome.handoff";
 NSString* const kOriginKey = @"kOriginKey";
 NSString* const kOriginiOS = @"kOriginiOS";
 NSString* const kOriginMac = @"kOriginMac";
 
 Origin OriginFromString(NSString* string) {
   if ([string isEqualToString:kOriginiOS])
     return ORIGIN_IOS;
 
   if ([string isEqualToString:kOriginMac])
     return ORIGIN_MAC;
 
   return ORIGIN_UNKNOWN;
 }
 
+NSString* StringFromOrigin(Origin origin) {
+  switch (origin) {
+    case ORIGIN_IOS:
+      return kOriginiOS;
+    case ORIGIN_MAC:
+      return kOriginMac;
+    default:
+      return nil;
+  }
+}
+
 }  // namespace handoff