Reviewed by Ryosuke Niwa.

        Get rid of firstDeepEditingPositionForNode and lastDeepEditingPositionForNode
        https://bugs.webkit.org/show_bug.cgi?id=52642

        Replacing calls to first/lastDeepEditingPositionForNode with calls to their analogous
        functions that create new positions. Also fixing various parts of editing code that
        incorrectly handled the new positions now being created.

        No new tests as this is refactoring/cleanup.

        * accessibility/AccessibilityRenderObject.cpp:
        (WebCore::AccessibilityRenderObject::visiblePositionRange):
        * dom/Position.cpp:
        (WebCore::Position::parentAnchoredEquivalent):
        (WebCore::Position::previous):
        (WebCore::Position::next):
        (WebCore::Position::atFirstEditingPositionForNode):
        (WebCore::Position::atLastEditingPositionForNode):
        (WebCore::Position::upstream):
        (WebCore::Position::isCandidate):
        (WebCore::Position::getInlineBoxAndOffset):
        * dom/Position.h:
        (WebCore::operator==):
        * dom/PositionIterator.cpp:
        (WebCore::PositionIterator::operator Position):
        * editing/ApplyBlockElementCommand.cpp:
        (WebCore::ApplyBlockElementCommand::rangeForParagraphSplittingTextNodesIfNeeded):
        * editing/CompositeEditCommand.cpp:
        (WebCore::CompositeEditCommand::positionAvoidingSpecialElementBoundary):
        * editing/DeleteSelectionCommand.cpp:
        (WebCore::isTableCellEmpty):
        (WebCore::DeleteSelectionCommand::removeNode):
        * editing/InsertLineBreakCommand.cpp:
        (WebCore::InsertLineBreakCommand::doApply):
        * editing/InsertListCommand.cpp:
        (WebCore::InsertListCommand::unlistifyParagraph):
        * editing/ReplaceSelectionCommand.cpp:
        (WebCore::ReplaceSelectionCommand::positionAtEndOfInsertedContent):
        * editing/TypingCommand.cpp:
        (WebCore::TypingCommand::forwardDeleteKeyPressed):
        * editing/VisibleSelection.cpp:
        (WebCore::VisibleSelection::selectionFromContentsOfNode):
        (WebCore::VisibleSelection::adjustSelectionToAvoidCrossingEditingBoundaries):
        * editing/htmlediting.cpp:
        (WebCore::firstEditablePositionAfterPositionInRoot):
        (WebCore::lastEditablePositionBeforePositionInRoot):
        (WebCore::enclosingEmptyListItem):
        * editing/htmlediting.h:
        * editing/visible_units.cpp:
        (WebCore::startOfParagraph):
        (WebCore::endOfParagraph):
        (WebCore::startOfEditableContent):
        (WebCore::endOfEditableContent):
        * rendering/RenderBox.cpp:
        (WebCore::RenderBox::positionForPoint):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@81165 268f45cc-cd09-0410-ab3c-d52691b4dbfc