[NTP::Cleanup] Store tab id as int in SnippetArticle.

components/ntp_snippets/offline_pages/recent_tab_suggestions_provider_unittest.cc

 // Copyright 2016 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.
 
 #include "components/ntp_snippets/offline_pages/recent_tab_suggestions_provider.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 21 matching lines @@
 using testing::IsEmpty;
 using testing::Mock;
 using testing::Property;
 using testing::SizeIs;
 
 namespace ntp_snippets {
 
 namespace {
 
 OfflinePageItem CreateDummyRecentTab(int id) {
-  return test::CreateDummyOfflinePageItem(id, offline_pages::kLastNNamespace);
+  OfflinePageItem item =
+      test::CreateDummyOfflinePageItem(id, offline_pages::kLastNNamespace);
+  item.client_id.id = base::IntToString(id);
+  return item;
 }
 
 std::vector<OfflinePageItem> CreateDummyRecentTabs(
     const std::vector<int>& ids) {
   std::vector<OfflinePageItem> result;
   for (int id : ids) {
     result.push_back(CreateDummyRecentTab(id));
   }
   return result;
 }
@@ skipping 274 matching lines @@
       *observer(),
       OnNewSuggestions(
           _, recent_tabs_category(),
           UnorderedElementsAre(
               Property(&ContentSuggestion::url, GURL("http://dummy.com/1")),
               Property(&ContentSuggestion::url, GURL("http://dummy.com/2")))));
   AddOfflinePageToModel(CreateDummyRecentTab(2));
 }
 
 }  // namespace ntp_snippets