libdot 1.2: Add export/import methods to lib.PreferenceManager.

* Add lib.PreferenceManager..exportAsJson/importFromJson methods to facilitate
  backup or migration of preferences.

BUG=None
TEST=Manual testing in nassh.

Change-Id: Iba4108054636de32a935edec8941138c31ac9989
Reviewed-on: https://gerrit.chromium.org/gerrit/47196
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
Commit-Queue: Robert Ginda <rginda@chromium.org>
Tested-by: Robert Ginda <rginda@chromium.org>
2 files changed
tree: d2b0fd16f8ad2af27f9237f6fd983615743693dd
  1. crosh_builtin/
  2. hterm/
  3. libdot/
  4. nassh/