Show empty options in shortcut chooser dialog if shortPreference is unchecked.

* Fix the magnification can not auto restore shortcut options.
* The shortcut chooser dialog behavior will be:
1. If user's toggle switch is turned off, and they open the shortcut chooser dialog, none of the options are selected. In this state, if user chooses some of the shortcuts and saves, these choices will be honored.
2. If user's toggle switch is turned off, and they turn on the switch without opening the shortcut chooser dialog, their previously-saved shortcut option is brought back (e.g. if I previously used a11y button, I turn toggle switch off and then on again, I still have a11y button).
3. If user's toggle switch is turned on, and they open the shortcut chooser dialog, their previously-saved shortcut options will be shown.

Bug: 152539702
Bug: 153042341
Test: manual test
Change-Id: Ic109b3363eaf00ba77ce0ed05f4ec11517b1367e