Add information about sync session and other useful data to about:sync.

chrome/browser/sync/syncable/syncable.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_H_
 #define CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_H_
 #pragma once
 
 #include <algorithm>
 #include <bitset>
@@ skipping 752 matching lines @@
   bool good() const { return NULL != store_; }
 
   // The download progress is an opaque token provided by the sync server
   // to indicate the continuation state of the next GetUpdates operation.
   void GetDownloadProgress(
       ModelType type,
       sync_pb::DataTypeProgressMarker* value_out) const;
   void GetDownloadProgressAsString(
       ModelType type,
       std::string* value_out) const;
+  size_t GetEntriesCount() const;
   void SetDownloadProgress(
       ModelType type,
       const sync_pb::DataTypeProgressMarker& value);
 
   bool initial_sync_ended_for_type(ModelType type) const;
   void set_initial_sync_ended_for_type(ModelType type, bool value);
   AutofillMigrationState get_autofill_migration_state() const;
 
   AutofillMigrationDebugInfo get_autofill_migration_debug_info() const;
 
@@ skipping 389 matching lines @@
 
 // This is not a reset.  It just sets the numeric fields which are not
 // initialized by the constructor to zero.
 void ZeroFields(EntryKernel* entry, int first_field);
 
 }  // namespace syncable
 
 std::ostream& operator <<(std::ostream&, const syncable::Blob&);
 
 #endif  // CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_H_