Do not show toast when coming from PreviewFragment

TopLevelPickerActivity shows a Toast to confirm wallpaper
has been set successfully, and PreviewFragment also shows it
(as it could be called from other, Activities).
So in TopLevelPickerActivity, when coming from
PreviewFragment, we don't want to show the Toast as it was
already shown once.

Fixes: 123589179
Change-Id: I218e743e7873c13e42d7018a54c2fc4099569de5
1 file changed