Add new method `historyGo`, that will let
the user navigate to a specific page from session history identified by its
relative position to the current page.
We add some tests to `location_spec.ts` to validate the behavior of the
`historyGo` and `forward` methods.
Add more tests for `location_spec` to test `location.historyGo(0)`, `location.historyGo()`,
`location.historyGo(100)` and `location.historyGo(-100)`. We also add new tests for
`Integration` spec to validate the navigation when we using
`location#historyGo`.
Update the `historyGo` function docs
Note that this was made an optional function in the abstract classes to
avoid a breaking change. Because our location classes use `implements PlatformLocation`
rather than `extends PlatformLocation`, simply adding a default
implementation was not sufficient to make this a non-breaking change.
While we could fix the classes internal to Angular, this would still have been
a breaking change for any external developers who may have followed our
implementations as an example.
PR Close#38890
e05a6f3bb3