Reviewed by Chris

    Reviewed by Chris

        Fix for this bug:

        <rdar://problem/3986155> Insertion point goes to beginning of doc after deleting

        * khtml/editing/htmlediting.cpp:
        (khtml::DeleteSelectionCommand::setStartNode): New convenience to handle reference counting when setting.
        (khtml::DeleteSelectionCommand::handleGeneralDelete): This contains the crux of the bug fix. Improve tests
        that detect when a selected node needs to be retained, rather than deleted, to preserve the intent of the user.
        This has the side effect of causing the insertion point placement code to succeed rather than fail. Before
        this fix, the failure of the insertion point placement code caused the insertion point to jump to the start
        of the document, which is the symptom that can be perceived by users when editing.
        * khtml/editing/htmlediting.h: Add setStartNode declaration.
        * khtml/editing/visible_units.cpp:
        (khtml::startOfBlock): This function had a stubbed-in non-tested implementation. Implement and
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-001-expected.txt: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-001.html: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-002-expected.txt: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-002.html: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-003-expected.txt: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-003.html: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-004-expected.txt: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-004.html: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-005-expected.txt: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-005.html: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-006-expected.txt: Added.
        * layout-tests/editing/deleting/delete-at-paragraph-boundaries-006.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8524 268f45cc-cd09-0410-ab3c-d52691b4dbfc