Reviewed by Simon Fraser.
        Patch by Antonio Gomes <tonikitoo@webkit.org>

        Spatial Navigation: Initial code simplification in FocusController.cpp and SpatialNavigation.cpp

        WebCore::distanceInDirection method was handling much of the logic not
        strictly only related to the distance between nodes acquisition. This
        method was simplified and renamed to 'WebCore::distanceDataForNode'.
        The latter is now responsible for only getting the distance and alignment
        data, while all assignement logic previously in distanceInDirection method
        was moved place to updateFocusCandidateIfCloser.

        Parent document distance and alignment acquisitions, in turn, have also
        changed location: they are both got from deepFindFocusableNodeInDirection,
        and passed in a recursive call to findFocusableNodeInDirection via the
        candidateParent variable (optional parameter). In addition, the need for
        the 'focusCandidateCopy' variable in deepFindFocusableNodeInDirection method
        was removed, making the code much cleaner.

        No behaviour change at this point. Mostly moving code around to the place
        where it should live in.

        * page/FocusController.cpp:
        (WebCore::FocusController::advanceFocusDirectionally):
        (WebCore::updateFocusCandidateIfCloser):
        (WebCore::FocusController::findFocusableNodeInDirection):
        (WebCore::FocusController::deepFindFocusableNodeInDirection):
        * page/FocusController.h:
        * page/SpatialNavigation.cpp:
        (WebCore::distanceDataForNode):
        (WebCore::renderRectRelativeToRootDocument):
        * page/SpatialNavigation.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@57061 268f45cc-cd09-0410-ab3c-d52691b4dbfc