Persist Directory to disk when the app is backgrounded.

chrome/browser/sync/glue/sync_backend_host.h

 // 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.
 
 #ifndef CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_
 #define CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 167 matching lines @@
 
   // True if the cryptographer has any keys available to attempt decryption.
   // Could mean we've downloaded and loaded Nigori objects, or we bootstrapped
   // using a token previously received.
   virtual bool IsCryptographerReady(
       const syncer::BaseTransaction* trans) const = 0;
 
   virtual void GetModelSafeRoutingInfo(
       syncer::ModelSafeRoutingInfo* out) const = 0;
 
+  // Send a message to the sync thread to persist the Directory to disk.
+  virtual void FlushDirectory() const = 0;
+
   // Requests that the backend forward to the fronent any protocol events in
   // its buffer and begin forwarding automatically from now on.  Repeated calls
   // to this function may result in the same events being emitted several
   // times.
   virtual void RequestBufferedProtocolEventsAndEnableForwarding() = 0;
 
   // Disables protocol event forwarding.
   virtual void DisableProtocolEventForwarding() = 0;
 
   // Returns a ListValue representing all nodes for the specified types through
@@ skipping 12 matching lines @@
   virtual void DisableDirectoryTypeDebugInfoForwarding() = 0;
 
   virtual base::MessageLoop* GetSyncLoopForTesting() = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_