This should enable to destinguish between IFrame, Reload and Navigation
motivated loads in order to call the appropriate hooks.
This change is motivated as loading the IFrame test page causes the
IFrame url to be added to the history and shows up as the current
browser location bar.
Activating a "#foo" fragment link will now be handled internally by
the Frame instead of involving the widget layer.
If the viewport needs to be scrolled as a result, we will simply ask
the PageClient to scroll a new rect into view.
* A PageView is a view onto a Page object.
* A Page always has a main Frame (root of Frame tree.)
* Page has a PageClient. PageView is a PageClient.
The goal here is to allow building another kind of view onto
a Page while keeping the rest of LibWeb intact.
