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

components/offline_pages/proto/offline_pages.proto

 // Copyright 2015 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.
 //
 // Offline page item protocol for storage and exchanging of offline page
 // metadata.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 option retain_unknown_fields = true;
 
 package offline_pages;
 
+// ClientID represents an identified in the API Client's namespace.  It is mapped to an offline_id which

[Dmitry Titov, 2016/02/12 21:46:51]

Is there a need to map this client-provided info into offline_id? I'd rather
not, because we want the offline_id to be unique and that's it. The data
provided by clients is the client's business. For example, "Last N pages"
feature would simply provide namespace and empty id since it does not need to
store additional data separately.

I think we should just autogenerate offline_id rather that compute it form
ClientId.

[bburns, 2016/02/20 01:14:18]

Done.

+// serves as the primary key for offline storage.
+message ClientId {
+  optional string space = 1;
+  optional string id = 2;
+}
+
 message OfflinePageEntry {
   // URL of the offline page.
-  required string url = 1;
+  optional string url = 1;
 
   // Bookmark ID of the offline page.
-  required int64 bookmark_id = 2;
+  optional int64 deprecated_bookmark_id = 2;
+
+  // Offline ID of the page.  Offline ID has replaced Bookmark ID as the primary key
+  optional int64 offline_id = 10;
 
   // Version of the offline page metadata.
-  required int32 version = 3;
+  optional int32 version = 3;
 
   // Path to the offline archive.
-  required string file_path = 4;
+  optional string file_path = 4;
 
   // Size of the offline archive.
   optional int64 file_size = 5;
 
   // Creation time of the offline archive.
   optional int64 creation_time = 6;
 
   // Last access time of the offline archive.
   optional int64 last_access_time = 7;
 
   // Number of times that the offline archive has been accessed.
   optional int32 access_count = 8;
 
   // Flags about the state and behavior of the offline page.
   enum Flags {
     // No flag is set.
     NONE = 0;
     // Indicates that the page is marked for deletion. The real deletion will
     // occur soon, after which the undo will not be possible.
     MARKED_FOR_DELETION = 1;
   };
 
   // Flags for the offline page.
   optional Flags flags = 9;
+
+  // ClientID for this entry, used for reverse lookups.
+  optional ClientId client_id = 11;
 }