filterRootById accidentally clears inAdjacentChain flag
https://bugs.webkit.org/show_bug.cgi?id=136851

Reviewed by Benjamin Poulain.

Source/WebCore:

Test: fast/selectors/filter-root-node-with-selector-contains-adjacents.html

* dom/SelectorQuery.cpp:
(WebCore::filterRootById):

LayoutTests:

When SubSelector comes, `inAdjacentChain` flag is cleared to false.
So for example, `document.querySelector("span#id + ok")` doesn't work correctly.
In this patch, we handles SubSelector relation correctly; don't change `inAdjacentChain` flag
to filter the right search root node.

* fast/selectors/filter-root-node-with-selector-contains-adjacents-expected.txt: Added.
* fast/selectors/filter-root-node-with-selector-contains-adjacents.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@173688 268f45cc-cd09-0410-ab3c-d52691b4dbfc