Because NDEFRecord#lang is supposed to be set to the document element's
lang attribute in the original web page that constructs/writes this
record, not in the current web page trying to construct an
NDEFReadingEvent instance.

This CL adds a wpt to guarantee that.

BUG=520391

Change-Id: If609455d6411ee886b74ab7557292c37da41eed6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930451
Reviewed-by: François Beaufort <[email protected]>
Commit-Queue: Leon Han <[email protected]>
Cr-Commit-Position: refs/heads/master@{#719855}