Remove NodeList's anonymous named getter

Remove NodeList's anonymous named getter as this is not part of the
specification:
http://dom.spec.whatwg.org/#nodelist

The new behavior is consistent with Firefox 26 and IE11. This was tested using:
http://jsfiddle.net/HQ5Nf/3/

NodeList's named getter used to get needed when getElementsByClassName() /
getElementsByTagName*() wrongly returned a NodeList instead of an
HTMLCollection. However, this has been fixed in r166263. HTMLCollection does
have an anonymous named getter.

BUG=235008
R=arv, haraken, tkent

Review URL: https://codereview.chromium.org/144313014

git-svn-id: svn://svn.chromium.org/blink/trunk@166356 bbb929c8-8fbe-4397-9dbb-9b2b20218538