Reviewed by Ken and Harrison.

    Reviewed by Ken and Harrison.

        - fixed <rdar://problem/3947901> REGRESSION (Mail): Pasting paragraph of rich text leaves insertion point before pasted text
        - fixed <rdar://problem/3949790> hitting return after underlined line results in too much or too little underlined
        - fixed <rdar://problem/3981759> nil-deref and crash when pasting just a paragraph break
        - fixed a couple problems I discovered while working with bug 3949790

        * khtml/editing/htmlediting.cpp:
        (khtml::ApplyStyleCommand::applyInlineStyle): Pass StayInBlock to upstream. Without this, we end up going too far
        upstream in the test case in bug 3949790.
        (khtml::ApplyStyleCommand::removeInlineStyle): Pass StayInBlock to upstream and downstream. Same reason as above.
        (khtml::ReplaceSelectionCommand::doApply): Update endPos if inserting a new node and endPos is using that node's
        parent and an offset past the node being inserted. That change fixes a problem with the position of the insertion point
        after pasting into the top level of a document (from test cases in 3947901 and 3949790). When setting insertionPos, use
        code that works when lastNodeInserted is a block rather than a text node. That change fixes a problem where a newline is
        not added when pasting an entire paragraph into the end of a document (from test case in 3949790). Added nil check before
        checking if lastNodeInserted is a <br> element, which fixes the crash when pasting just a paragraph break.

        * khtml/editing/visible_units.h: Filled out the set of calls to add some boolean checks for lines (needed for the
        bug fix), and calls for blocks (not yet implemented), and documents. The document checks may need refinement to
        properly handle documents with a mix of editable and non-editable content, but for now they just refactor code
        and make things a little clearer. Also removed the "include line break" parameter from endOfSentence.
        * khtml/editing/visible_units.cpp:
        (khtml::rootBoxForLine): Added.
        (khtml::startOfLine): Added. Algorithm taken from selectionForLine in selection.cpp.
        (khtml::endOfLine): Ditto.
        (khtml::inSameLine): Added.
        (khtml::isStartOfLine): Added.
        (khtml::isEndOfLine): Added.
        (khtml::endOfSentence): Removed "include line break" parameter.
        (khtml::inSameParagraph): Added a null check.
        (khtml::isStartOfParagraph): Ditto.
        (khtml::isEndOfParagraph): Ditto.
        (khtml::startOfBlock): Added.
        (khtml::endOfBlock): Added.
        (khtml::inSameBlock): Added.
        (khtml::isStartOfBlock): Added.
        (khtml::isEndOfBlock): Added.
        (khtml::startOfDocument): Added.
        (khtml::endOfDocument): Added.
        (khtml::inSameDocument): Added.
        (khtml::isStartOfDocument): Added.
        (khtml::isEndOfDocument): Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8480 268f45cc-cd09-0410-ab3c-d52691b4dbfc