[Offline Pages] Add a GCMAppHandler for offline page prefetch.

components/offline_pages/core/prefetch/BUILD.gn

 # Copyright 2017 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.
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 import("//third_party/protobuf/proto_library.gni")
 
 static_library("prefetch") {
   sources = [
     "generate_page_bundle_request.cc",
     "generate_page_bundle_request.h",
+    "prefetch_gcm_app_handler.cc",
+    "prefetch_gcm_app_handler.h",
     "prefetch_item.cc",
     "prefetch_item.h",
     "prefetch_request_fetcher.cc",
     "prefetch_request_fetcher.h",
     "prefetch_service.h",
     "prefetch_service_impl.cc",
     "prefetch_service_impl.h",
     "prefetch_types.cc",
     "prefetch_types.h",
     "prefetch_utils.cc",
     "prefetch_utils.h",
+    "suggested_articles_observer.cc",
+    "suggested_articles_observer.h",
   ]
 
   public_deps = [
     ":proto",
   ]
   deps = [
     "//base",
+    "//components/gcm_driver",
+    "//components/gcm_driver/common",
     "//components/keyed_service/core",
+    "//components/ntp_snippets",
     "//components/offline_pages/core",
+    "//components/offline_pages/core:switches",
     "//net:net",
     "//url",
   ]
 }
 
 proto_library("proto") {
   sources = [
     "proto/any.proto",
     "proto/offline_pages.proto",
     "proto/operation.proto",
     "proto/status.proto",
     "proto/timestamp.proto",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "generate_page_bundle_request_unittest.cc",
     "prefetch_item_unittest.cc",
     "prefetch_request_fetcher_unittest.cc",
     "prefetch_request_test_base.cc",
     "prefetch_request_test_base.h",
     "prefetch_service_impl_unittest.cc",
+    "suggested_articles_observer_unittest.cc",
   ]
 
   deps = [
     ":prefetch",
     "//components/offline_pages/core",
+    "//components/offline_pages/core:test_support",
     "//net:test_support",
     "//testing/gmock",
     "//testing/gtest",
     "//url",
   ]
 }