Introduce a request throttler for limiting requests in mobile NTP.

components/ntp_snippets.gypi

 # Copyright 2015 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.
 
 {
   'targets': [
     {
       # GN version: //components/ntp_snippets
       'target_name': 'ntp_snippets',
       'type': 'static_library',
@@ skipping 35 matching lines @@
         'ntp_snippets/ntp_snippets_fetcher.cc',
         'ntp_snippets/ntp_snippets_fetcher.h',
         'ntp_snippets/ntp_snippets_scheduler.h',
         'ntp_snippets/ntp_snippets_service.cc',
         'ntp_snippets/ntp_snippets_service.h',
         'ntp_snippets/ntp_snippets_status_service.cc',
         'ntp_snippets/ntp_snippets_status_service.h',
         'ntp_snippets/pref_names.cc',
         'ntp_snippets/pref_names.h',
         'ntp_snippets/proto/ntp_snippets.proto',
+        'ntp_snippets/request_counter.cc',
+        'ntp_snippets/request_counter.h',
         'ntp_snippets/switches.cc',
         'ntp_snippets/switches.h',
       ],
       'variables': {
         'proto_in_dir': 'ntp_snippets/proto',
         'proto_out_dir': 'components/ntp_snippets/proto',
       },
       'includes': [ '../build/protoc.gypi' ],
     },
   ],
 }