Show icon in PendingAppWidgetHostView immediately.

Before this change, PendingAppWidgetHostView would appear 'blank'
until they were loaded -- which could take a while depending on
how many apps the user had, because the all apps icons are loaded
first.

Bug: 36815047
Change-Id: Ia7449cce4341ed9e9384fc8aaadeaae6c33bb262