Drop [LegacyInterfaceTypeChecking] for Selection.prototype.addRange

This already throws in Firefox and IE11 when the argument is null:
http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3781

DOMSelection::addRange is only called from generated bindings, so the
assert will hold.

BUG=561338

Review URL: https://codereview.chromium.org/1511913002

Cr-Commit-Position: refs/heads/master@{#364322}
4 files changed