Reviewed by Maciej.

    Reviewed by Maciej.

        - http://bugzilla.opendarwin.org/show_bug.cgi?id=8210
        Conditional XMLHttpRequest gets should pass 304 responses unchanged

        Test: http/tests/xmlhttprequest/cache-override.html

        * Misc/WebNSURLRequestExtras.h: Added _web_isConditionalRequest
        * Misc/WebNSURLRequestExtras.m:
        (-[NSURLRequest _web_isConditionalRequest]):
        * WebCoreSupport/WebFrameBridge.m:
        (-[WebFrameBridge syncLoadResourceWithMethod:URL:customHeaders:postData:finalURL:responseHeaders:statusCode:]):
        Bypass the cache for conditional requests.
        * WebCoreSupport/WebSubresourceLoader.m:
        (+[WebSubresourceLoader startLoadingResource:withRequest:customHeaders:referrer:forDataSource:]): Ditto.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@15150 268f45cc-cd09-0410-ab3c-d52691b4dbfc