[Offline Pages] Adds Rappor metrics measuring what domains are saved & viewed.

chrome/browser/android/offline_pages/offline_page_model_factory.cc

Index: chrome/browser/android/offline_pages/offline_page_model_factory.cc
diff --git a/chrome/browser/android/offline_pages/offline_page_model_factory.cc b/chrome/browser/android/offline_pages/offline_page_model_factory.cc
index b9992863bb75c8d541336717ca4e23ac939b7316..c8206a6bd8cc1e4c35fcf4a301b4eef09116b9d2 100644
--- a/chrome/browser/android/offline_pages/offline_page_model_factory.cc
+++ b/chrome/browser/android/offline_pages/offline_page_model_factory.cc
@@ -9,6 +9,7 @@
 #include "base/files/file_path.h"
 #include "base/memory/singleton.h"
 #include "base/sequenced_task_runner.h"
+#include "chrome/browser/browser_process.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_constants.h"
@@ -16,6 +17,7 @@
 #include "components/offline_pages/offline_page_metadata_store_sql.h"
 #include "components/offline_pages/offline_page_model.h"
 #include "components/offline_pages/proto/offline_pages.pb.h"
+#include "components/rappor/rappor_service.h"
 #include "content/public/browser/browser_thread.h"
 
 namespace offline_pages {
@@ -54,6 +56,7 @@ KeyedService* OfflinePageModelFactory::BuildServiceInstanceFor(
       profile->GetPath().Append(chrome::kOfflinePageArchviesDirname);
 
   return new OfflinePageModel(std::move(metadata_store), archives_dir,
+                              g_browser_process->rappor_service()->AsWeakPtr(),
                               background_task_runner);
 }