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

components/offline_pages/offline_page_model.h

Index: components/offline_pages/offline_page_model.h
diff --git a/components/offline_pages/offline_page_model.h b/components/offline_pages/offline_page_model.h
index 90ed8bfbe1ad4a2b63a99b0904d76cee594b186d..06c88ba451e42c8e9b13e98a5de3e66739f85407 100644
--- a/components/offline_pages/offline_page_model.h
+++ b/components/offline_pages/offline_page_model.h
@@ -33,6 +33,9 @@ class Time;
 class TimeDelta;
 class TimeTicks;
 }
+namespace rappor {
+class RapporService;
+}
 
 namespace offline_pages {
 
@@ -156,6 +159,7 @@ class OfflinePageModel : public KeyedService, public base::SupportsUserData {
   // All blocking calls/disk access will happen on the provided |task_runner|.
   OfflinePageModel(std::unique_ptr<OfflinePageMetadataStore> store,
                    const base::FilePath& archives_dir,
+                   base::WeakPtr<rappor::RapporService> rappor_service,
                    const scoped_refptr<base::SequencedTaskRunner>& task_runner);
   ~OfflinePageModel() override;
 
@@ -407,6 +411,8 @@ class OfflinePageModel : public KeyedService, public base::SupportsUserData {
   // automatic page clearing.
   std::unique_ptr<OfflinePageStorageManager> storage_manager_;
 
+  base::WeakPtr<rappor::RapporService> rappor_service_;
+
   base::WeakPtrFactory<OfflinePageModel> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageModel);