res:dock:: fix wrong size problem.

1. item gets wrong size after client is closed.
2. app_list gets wrong size after switch mode or add/delete applets.

reason:
1. webkit will ignore width after the element is expanded by -webkit-box-flex:1.
2. not update app_list's width on the right time.

solution:
1. do not display the element and show it later, force webkit to using width.
2. update app_list's width.

Change-Id: I7ce1e1bfb3a39e192c4892aded47b30cdcc17e23