Reviewed by John

    Reviewed by John

        Fix for this bug:

        <rdar://problem/3928305> selecting an entire line and typing over causes new inserted text at top of document

        * khtml/editing/htmlediting.cpp:
        (khtml::DeleteSelectionCommand::insertPlaceholderForAncestorBlockContent): New function to detect case
        formerly undetected and unhandled. This is the crux of the bug fix.
        (khtml::DeleteSelectionCommand::doApply): Call insertPlaceholderForAncestorBlockContent() during
        execution of command.
        * khtml/editing/htmlediting.h: Declare new function.
        * layout-tests/editing/deleting/delete-3928305-fix-expected.txt: Added.
        * layout-tests/editing/deleting/delete-3928305-fix.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8271 268f45cc-cd09-0410-ab3c-d52691b4dbfc