nfc: Implement NfcAdapterChromeOS.

Added the basic implementation of NfcAdapterChromeOS, with no tag/peer logic.

BUG=316471
TEST=device_unittests

Review URL: https://codereview.chromium.org/100393011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239388 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239388