[Popular Sites] Add Variations parameter to override URL path

components/ntp_tiles/pref_names.cc

 // Copyright 2016 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/ntp_tiles/pref_names.h"
 
 namespace ntp_tiles {
 namespace prefs {
 
 // The number of personal tiles we had previously. Used to figure out
 // whether we need popular sites.
 const char kNumPersonalTiles[] = "ntp.num_personal_suggestions";
 
 // If set, overrides the URL for popular sites, including the individual
 // overrides for country and version below.
 const char kPopularSitesOverrideURL[] = "popular_sites.override_url";
 
+// If set, this will override the URL path directory for popular sites.
+const char kPopularSitesOverrideDirectory[] =
+    "popular_sites.override_directory";
+
 // If set, this will override the country detection for popular sites.
 const char kPopularSitesOverrideCountry[] = "popular_sites.override_country";
 
 // If set, this will override the default file version for popular sites.
 const char kPopularSitesOverrideVersion[] = "popular_sites.override_version";
 
 }  // namespace prefs
 }  // namespace ntp_tiles