Slap ALWAYS_INLINE on Element attribute lookup things.

Slap ALWAYS_INLINE on Element attribute lookup things.
<https://webkit.org/b/131892>

Most of the "inline" helpers for setting/getting attributes were not
actually getting inlined by the compiler, so let's make that happen.

Reviewed by Geoffrey Garen.

* dom/Element.cpp:
(WebCore::Element::synchronizeAttribute):
* dom/ElementData.h:
(WebCore::ElementData::findAttributeByName):
(WebCore::ElementData::findAttributeIndexByName):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@167545 268f45cc-cd09-0410-ab3c-d52691b4dbfc