RS by Darin.

    RS by Darin.

        Rolled out change to map NULL Strings to nil NSStrings because it caused
        even more AppKit crashes. Maybe we should remove the NSString * operator
        entirely, since its use is not straight-forward, and require callers to
        specify explicitly whether they tolerate NULL.

        * platform/AtomicString.h:
        * platform/PlatformString.h:
        (WebCore::String::operator NSString*):
        * platform/mac/TextFieldMac.mm:
        (-[NSSearchFieldCell _addStringToRecentSearches:]):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@17419 268f45cc-cd09-0410-ab3c-d52691b4dbfc