The `UrlTree` is a fundamental concept in the router's API design.
Generally speaking, a `UrlTree` would be constructed via things like
`Router.createUrlTree` or `UrlSerializer#parse`. The second example here
is the core reason to make the constructor public, regardless of how
develpers generally create a `UrlTree` in an application.
Applications can provide their own `UrlSerializer` and may want to implement their
own `parse` method. This means they would also need to create a
`UrlTree` but would not be able to do so effectively because the
constructor is marked `@internal`.
In addition, the `UrlTree` constructor only has 3 parameters, all of
which are already public. There's nothing "special" about it other than
the potential desire to push developers to use other methods for
constructing a `UrlTree` (i.e. `Router.createUrlTree`).
Also see http://b/234604699#comment9 for additional context.
PR Close#47186
5163e3d876