[webnfc] Align NFC interface with latest specification.

Based on review feedback, WebNFC specification was modified
and requestAdapter() method was removed from NFC interface.
Methods from NFCAdapter were moved to NFC interface.
This patch adds new methods to NFC interface and aligns
corresponding idl files with latest specification.

https://w3c.github.io/web-nfc/#dom-nfc-push
https://w3c.github.io/web-nfc/#dom-nfc-cancelpush
https://w3c.github.io/web-nfc/#dom-nfc-watch
https://w3c.github.io/web-nfc/#dom-nfc-cancelwatch

BUG=520391

Review URL: https://codereview.chromium.org/1444303002

Cr-Commit-Position: refs/heads/master@{#361085}
12 files changed