Bug 1115468 - Some attrubites of MozNFCTag are null. r=dimi

From bf11cb363f58cce8eff86c6234930a94834b3c11 Mon Sep 17 00:00:00 2001
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 dom/nfc/NfcContentHelper.js     | 40 ++++++++++++++++++++++++++++------------
 dom/nfc/nsINfcContentHelper.idl | 23 +++++++++++++++++------
 dom/nfc/nsNfc.js                | 38 ++++++++++++++++++++------------------
 3 files changed, 65 insertions(+), 36 deletions(-)