Add request throttler to thumbnail fetching for articles on mobile NTP

components/ntp_snippets/BUILD.gn

 # 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.
 
 import("//build/config/ui.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
@@ skipping 104 matching lines @@
     "//components/image_fetcher",
     "//components/leveldb_proto:test_support",
     "//components/signin/core/browser:test_support",
     "//components/signin/core/common",
     "//components/strings",
     "//components/sync:test_support_sync_driver",
     "//components/variations",
     "//net:test_support",
     "//testing/gtest",
     "//third_party/icu/",
+    "//ui/gfx:test_support",
   ]
 }