Do not convert to String->AtomicString for NamedNodeMap
https://bugs.webkit.org/show_bug.cgi?id=108289

Reviewed by Kentaro Hara.

NamedNodeMap's API was taking a WTF::String. Internally, attribute
names are AtomicString.

The conversions String->AtomicString was causing an additional ref-deref
for the JS/V8 bindings. And could cause an additional memory allocation for the Objective-C
bindings.

This patch changes the API to use AtomicString, and update the custom bindings accordingly.

* bindings/js/JSNamedNodeMapCustom.cpp:
(WebCore::JSNamedNodeMap::canGetItemsForName):
(WebCore::JSNamedNodeMap::nameGetter):
* bindings/v8/custom/V8NamedNodeMapCustom.cpp:
(WebCore::V8NamedNodeMap::namedPropertyGetter):
* dom/NamedNodeMap.cpp:
(WebCore::NamedNodeMap::getNamedItem):
(WebCore::NamedNodeMap::getNamedItemNS):
(WebCore::NamedNodeMap::removeNamedItem):
(WebCore::NamedNodeMap::removeNamedItemNS):
* dom/NamedNodeMap.h:
(NamedNodeMap):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141300 268f45cc-cd09-0410-ab3c-d52691b4dbfc