This CL also introduces Realm.navigate(i).

BUG=chromium:683667

Change-Id: I9227292ea3a575f34367e82fc6297d234d3eecae
Reviewed-on: https://chromium-review.googlesource.com/447638
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43494}