processed
   * the first time.
   *
   * @param aPrefBranch  Preferences branch to import from. The preferences
   *                     under this branch can specify whitelist (ALLOW_ACTION)
   *                     or blacklist (DENY_ACTION) additions using perference
   *                     names of the form:
   *                     * <BRANCH>.whitelist.add.<ID>
   *                     * <BRANCH>.blacklist.add.<ID>
   *                     Where <ID> can be any valid preference name.
   *                     The value is expected to be a comma separated list of
   *                     host named. eg:
   *                     * something.example.com
   *                     * foo.exmaple.com,bar.example.com
   *
   * @param aPermission Permission name to be passsed to the Permissions
   *                    Manager.
   */
  importFromPrefs(aPrefBranch, aPermission) {
    if (!aPrefBranch.endsWith(".")) {
      aPrefBranch += ".";
    }

    // Ensure we only import this pref branch once.
    if (gImportedPrefBranches.has(aPrefBranch)) {
      return;
    }

    importPrefBranch(
      aPrefBranch + "whitelist.add",
      aPermission,
      Services.perms.ALLOW_ACTION
    );
    importPrefBranch(
      aPrefBranch + "blacklist.add",
      aPermission,
      Services.perms.DENY_ACTION
    );

    gImportedPrefBranches.add(aPrefBranch);
  },
};

// For test use only.
export const PermissionsTestUtils = {
  clearImportedPrefBranches() {
    gImportedPrefBranches.clear();
  },
};
PK