[Popular Sites] Add Variations parameter to override URL path

components/ntp_tiles/popular_sites_impl_unittest.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/popular_sites_impl.h"
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 440 matching lines @@
   // Second request refetches ZZ_9, which now has data.
   RespondWithJSON(
       "https://www.gstatic.com/chrome/ntp/suggested_sites_ZZ_9.json",
       {kChromium});
   EXPECT_THAT(FetchPopularSites(/*force_download=*/false, &sites),
               Eq(base::Optional<bool>(true)));
   ASSERT_THAT(sites.size(), Eq(1u));
   EXPECT_THAT(sites[0].url, URLEq("https://www.chromium.org/"));
 }
 
+TEST_F(PopularSitesTest, ShouldOverrideDirectory) {
+  SetCountryAndVersion("ZZ", "9");
+  prefs_->SetString(prefs::kPopularSitesOverrideDirectory, "foo/bar/");
+  RespondWithJSON("https://www.gstatic.com/foo/bar/suggested_sites_ZZ_9.json",
+                  {kWikipedia});
+
+  PopularSites::SitesVector sites;
+  EXPECT_THAT(FetchPopularSites(/*force_download=*/false, &sites),
+              Eq(base::Optional<bool>(true)));
+
+  EXPECT_THAT(sites.size(), Eq(1u));
+}
+
 }  // namespace
 }  // namespace ntp_tiles