Add ContentSuggestionsService

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.
 
 # GYP version: components/ntp_snippets.gypi:ntp_snippets
 source_set("ntp_snippets") {
   sources = [
     "content_suggestion.cc",
     "content_suggestion.h",
     "content_suggestion_category.h",
+    "content_suggestions_provider.h",
     "content_suggestions_provider_type.h",
+    "content_suggestions_service.cc",
+    "content_suggestions_service.h",
     "ntp_snippet.cc",
     "ntp_snippet.h",
     "ntp_snippets_constants.cc",
     "ntp_snippets_constants.h",
     "ntp_snippets_database.cc",
     "ntp_snippets_database.h",
     "ntp_snippets_fetcher.cc",
     "ntp_snippets_fetcher.h",
     "ntp_snippets_scheduler.h",
     "ntp_snippets_service.cc",
@@ skipping 44 matching lines @@
     "//components/image_fetcher",
     "//components/leveldb_proto:test_support",
     "//components/signin/core/browser:test_support",
     "//components/sync_driver:test_support",
     "//components/variations",
     "//net:test_support",
     "//testing/gtest",
     "//third_party/icu/",
   ]
 }