Refactor the offline page storage to include client namespace and id.

components/offline_pages/offline_page_item.h

Index: components/offline_pages/offline_page_item.h
diff --git a/components/offline_pages/offline_page_item.h b/components/offline_pages/offline_page_item.h
index a7bf8c8fa1d3f9424aa941d2f64d3e98e63e5ab0..0b7218bdb40ea8d59f16fea8f804661107c2add1 100644
--- a/components/offline_pages/offline_page_item.h
+++ b/components/offline_pages/offline_page_item.h
@@ -16,6 +16,8 @@
 
 namespace offline_pages {
 
+class ClientId;
+
 // Metadata of the offline page.
 struct OfflinePageItem {
  public:
@@ -27,11 +29,13 @@ struct OfflinePageItem {
 
   OfflinePageItem();
   OfflinePageItem(const GURL& url,
-                  int64_t bookmark_id,
+                  int64_t offline_id,
+                  const ClientId& client_id,
                   const base::FilePath& file_path,
                   int64_t file_size);
   OfflinePageItem(const GURL& url,
-                  int64_t bookmark_id,
+                  int64_t offline_id,
+                  const ClientId& client_id,
                   const base::FilePath& file_path,
                   int64_t file_size,
                   const base::Time& creation_time);
@@ -50,8 +54,13 @@ struct OfflinePageItem {
 
   // The URL of the page.
   GURL url;
-  // The Bookmark ID related to the offline page.
-  int64_t bookmark_id;
+  // The Offline (internal) ID related to the offline page.
+  int64_t offline_id;
+
+  // The Client ID (external) related to the offline page.
+  std::string client_id_namespace;
+  std::string client_id;
+
   // Version of the offline page item.
   int version;
   // The file path to the archive with a local copy of the page.