Add special tree walking for the single tag or class CSS query selectors
https://bugs.webkit.org/show_bug.cgi?id=117388

Reviewed by Ryosuke Niwa.

Queries for a single tag name or a single class name are the most common
input of querySelector.

This patch adds a simplified tree walking in those cases, only checking that particular
case instead of a full selector.

With the change, the balanced query selector benchmarks become 11% faster.

* css/SelectorCheckerFastPath.cpp:
(WebCore::HTMLNames::checkClassValue):
* dom/SelectorQuery.cpp:
(WebCore::isSingleTagNameSelector):
(WebCore::SelectorDataList::executeSingleTagNameSelectorData):
(WebCore::isSingleClassNameSelector):
(WebCore::SelectorDataList::executeSingleClassNameSelectorData):
(WebCore::SelectorDataList::execute):
* dom/SelectorQuery.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@151365 268f45cc-cd09-0410-ab3c-d52691b4dbfc