Persist Directory to disk when the app is backgrounded.

chrome/browser/sync/profile_sync_service.h

Index: chrome/browser/sync/profile_sync_service.h
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index c16537e95289f906ec19a50153ca876407845b62..2aa7c95290b57b1434101f035f612bc26d8fb1ad 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -789,6 +789,11 @@ class ProfileSyncService : public ProfileSyncServiceBase,
 
   base::Time GetDeviceBackupTimeForTesting() const;
 
+  // This triggers a Directory::SaveChanges() call on the sync thread.
+  // It should be used to persist data to disk when the process might be
+  // killed in the near future.
+  void FlushDirectory() const;
+
  protected:
   // Helper to configure the priority data types.
   void ConfigurePriorityDataTypes();