Reviewed by Darin.

        - Added support for strings that masquerade as undefined. Currently used
        by WebCore to implement undetectable style.filter.
        
        The name is a little long, but it's only used in one line of code, so I
        thought clarity should win over brevity.

        * JavaScriptCore.exp:
        * JavaScriptCore.xcodeproj/project.pbxproj:
        * kjs/object.h:
        * kjs/string_object.h:
        (KJS::StringInstanceThatMasqueradesAsUndefined::StringInstanceThatMasqueradesAsUndefined):
        (KJS::StringInstanceThatMasqueradesAsUndefined::masqueradeAsUndefined):
        (KJS::StringInstanceThatMasqueradesAsUndefined::toBoolean):

LayoutTests:

        Test for undetectable style.filter property.

        * fast/dom/undetectable-style-filter-expected.txt: Added.
        * fast/dom/undetectable-style-filter.html: Added.

WebCore:

        Reviewed by Darin.
        
        - Fixed <rdar://problem/4507265> REGRESSION: overlays don't work on 
        HousingMaps.com (Google Maps-based site)
        
        - Made style.filter undetectable, like document.all.
        
        Unfortunately, the SVG spec-makers invented a CSS attribute named 'filter',
        which conflicts with IE's custom CSS attribute by the same name. Web programs 
        like the Google maps API test for style.filter, and assume it's the IE 
        style.filter if they find it, so we need to make style.filter undetectable 
        to avoid breaking them.
        
        An alternative solution would be to hotwire a delorean, go back in time,
        and beg the web standards makers to make standards that work on the web.

        * bindings/js/kjs_css.cpp:
        (KJS::DOMCSSStyleDeclaration::cssPropertyGetter):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@15557 268f45cc-cd09-0410-ab3c-d52691b4dbfc