[iOS] Cleanup unused pref names

ios/chrome/browser/pref_names.cc

 // 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 "ios/chrome/browser/pref_names.h"
 
 namespace ios {
 namespace prefs {
 
 // Preferences in ios::prefs:: must have the same value as the corresponding
@@ skipping 71 matching lines @@
 // for Omnibox queries or the progress towards soliciting the user's
 // authorization.
 extern const char kOmniboxGeolocationAuthorizationState[] =
     "ios.omnibox.geolocation_authorization_state";
 
 // String which contains the application version when we last showed the
 // authorization alert.
 extern const char kOmniboxGeolocationLastAuthorizationAlertVersion[] =
     "ios.omnibox.geolocation_last_authorization_alert_version";
 
-// Number of seconds from 1970 when the doodle expires.
-extern const char kDoodleExpirationTimeInSeconds[] =
-    "ios.doodle.expiration_time.seconds";
-
-// The URL to navigate to when the user taps the doodle.
-extern const char kDoodleHref[] = "ios.doodle.href";
-
-// Number of seconds from 1970 since the last time a doodle was requested.
-extern const char kDoodleLastRequestTimeInSeconds[] =
-    "ios.doodle.last_request_time.seconds";
-
-// The alternative text for the doodle.
-extern const char kDoodleAltText[] = "ios.doodle.alttext";
-
 }  // namespace prefs