contacts: Add UpdateMetadata protocol buffer.

chrome/browser/chromeos/contacts/contact.proto

 // Copyright (c) 2012 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.
 //
 // Protocol buffer definitions for the user's contacts.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
@@ skipping 79 matching lines @@
       ICQ = 6;
       JABBER = 7;
       OTHER = 8;
     }
     optional Protocol protocol = 2 [default = OTHER];
     optional AddressType type = 3;
     optional bool primary = 4 [default = false];
   }
   repeated InstantMessagingAddress instant_messaging_addresses = 14;
 }
+
+// Singleton message used by ContactDatabase to store update-related metadata.
+message UpdateMetadata {
+  // Next ID to use: 2
+
+  // Time at which the last successful update was started, as given by
+  // base::Time::ToInternalValue().
+  optional int64 last_update_start_time = 1;
+}