Introduce a request throttler for limiting requests in 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 18 matching lines @@
     "ntp_snippets_database.h",
     "ntp_snippets_fetcher.cc",
     "ntp_snippets_fetcher.h",
     "ntp_snippets_scheduler.h",
     "ntp_snippets_service.cc",
     "ntp_snippets_service.h",
     "ntp_snippets_status_service.cc",
     "ntp_snippets_status_service.h",
     "pref_names.cc",
     "pref_names.h",
+    "request_counter.cc",
+    "request_counter.h",
     "switches.cc",
     "switches.h",
   ]
 
   public_deps = [
     "//base",
     "//components/keyed_service/core",
     "//components/leveldb_proto",
     "//components/prefs",
     "//components/signin/core/browser",
@@ skipping 26 matching lines @@
 source_set("unit_tests") {
   testonly = true
   sources = [
     "ntp_snippet_unittest.cc",
     "ntp_snippets_database_unittest.cc",
     "ntp_snippets_fetcher_unittest.cc",
     "ntp_snippets_service_unittest.cc",
     "ntp_snippets_status_service_unittest.cc",
     "ntp_snippets_test_utils.cc",
     "ntp_snippets_test_utils.h",
+    "request_counter_unittest.cc",
   ]
 
   deps = [
     ":ntp_snippets",
     "//base",
     "//base/test:test_support",
     "//components/image_fetcher",
     "//components/leveldb_proto:test_support",
     "//components/signin/core/browser:test_support",
     "//components/signin/core/common",
     "//components/sync_driver:test_support",
     "//components/variations",
     "//net:test_support",
     "//testing/gtest",
     "//third_party/icu/",
   ]
 }