Live to the promise of never making AppKit special character codes visible via DOM.

        Test: fast/events/arrow-keys-on-body.html

        * page/EventHandler.cpp:
        (WebCore::EventHandler::keyEvent): Check for empty keypress characters after disambiguation,
        to let quirks-aware code strip special charactrers.
        * platform/mac/KeyEventMac.mm:
        (WebCore::PlatformKeyboardEvent::disambiguateKeyDownEvent): If not in keyboard event quirks
        mode, remove the text if it's a special character.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@28813 268f45cc-cd09-0410-ab3c-d52691b4dbfc