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

components/offline_pages/offline_page_model.cc

Index: components/offline_pages/offline_page_model.cc
diff --git a/components/offline_pages/offline_page_model.cc b/components/offline_pages/offline_page_model.cc
index 3472066eb9fa33f5dfd6b8b1633e85fee0041ffa..462f03aa5408d9248bc3311f458cdb6f99535555 100644
--- a/components/offline_pages/offline_page_model.cc
+++ b/components/offline_pages/offline_page_model.cc
@@ -22,6 +22,8 @@
 #include "components/offline_pages/offline_page_item.h"
 #include "components/offline_pages/offline_page_storage_manager.h"
 #include "components/offline_pages/proto/offline_pages.pb.h"
+#include "components/rappor/rappor_service.h"
+#include "components/rappor/rappor_utils.h"
 #include "url/gurl.h"
 
 using ArchiverResult = offline_pages::OfflinePageArchiver::ArchiverResult;
@@ -104,6 +106,16 @@ void EnsureArchivesDirCreated(const base::FilePath& archives_dir) {
   CHECK(base::CreateDirectory(archives_dir));
 }
 
+// Record a sample for the OfflinePages.SavedPage rappor metric.
+void SampleOfflinePageURL(
+    const GURL& url,
+    const base::WeakPtr<rappor::RapporService>& rappor_service) {
+  if (rappor_service && url.is_valid()) {
+    rappor::SampleDomainAndRegistryFromGURL(
+        rappor_service.get(), "OfflinePages.PageWasSavedForOffline", url);
+  }
+}
+
 }  // namespace
 
 // static
@@ -118,12 +130,14 @@ OfflinePageModel::OfflinePageModel()
 OfflinePageModel::OfflinePageModel(
     std::unique_ptr<OfflinePageMetadataStore> store,
     const base::FilePath& archives_dir,
+    base::WeakPtr<rappor::RapporService> rappor_service,
     const scoped_refptr<base::SequencedTaskRunner>& task_runner)
     : store_(std::move(store)),
       archives_dir_(archives_dir),
       is_loaded_(false),
       task_runner_(task_runner),
       policy_controller_(new ClientPolicyController()),
+      rappor_service_(rappor_service),
       weak_ptr_factory_(this) {
   task_runner_->PostTaskAndReply(
       FROM_HERE, base::Bind(EnsureArchivesDirCreated, archives_dir_),
@@ -157,6 +171,8 @@ void OfflinePageModel::SavePage(const GURL& url,
 
   DCHECK(archiver.get());
 
+  SampleOfflinePageURL(url, rappor_service_);
+
   int64_t offline_id = GenerateOfflineId();
 
   archiver->CreateArchive(