Restores previously saved scroll positions.
If no earlier scroll position is known, scroll positions are not changed and false is returned.
false
Unpoly automatically restores scroll positions when the user presses the back button.
The viewports for which to restore scroll positions.
Defaults to all viewports within the given layer.
The layer on which to restore scroll positions.
The URL for which to restore scroll positions.
If omitted, the given layer's location is used.
Returns whether scroll positions could be restored.
