Reviewed by Mitz.

        - fix <rdar://problem/5726016> REGRESSION: Xcode News window renders
          incorrectly due to visibility fix

        Added an Xcode-specific quirk.

        * WebCore.base.exp: Added export for new Settings function.
        * css/CSSMutableStyleDeclaration.cpp:
        (WebCore::CSSMutableStyleDeclaration::setProperty): Here's the crazy quirk.
        If you try to change the visibilty on a node with the class name tab_content,
        instead it will use display:none.
        * page/Settings.cpp:
        (WebCore::Settings::Settings): Initialize m_needsXcodeVisibilityQuirk. Also
        initialize m_fontRenderingMode! This seems like it was a bug before, but we
        probably were getting lucky and always getting 0 on Windows, which is the
        only place the setting matters.
        (WebCore::Settings::setNeedsXcodeVisibilityQuirk): Added.
        * page/Settings.h:
        (WebCore::Settings::needsXcodeVisibilityQuirk): Added.

WebKit/mac:

        Reviewed by Mitz.

        - fix <rdar://problem/5726016> REGRESSION: Xcode News window renders
          incorrectly due to visibility fix

        Added an Xcode-specific quirk.

        * Misc/WebKitVersionChecks.h: Added a constant for the "linked on or after"
        part of the check.

        * WebView/WebView.mm:
        (-[WebView _needsXcodeVisibilityQuirk]): Added.
        (-[WebView _preferencesChangedNotification:]): Added a call to
        setNeedsXcodeVisibilityQuirk based on _needsXcodeVisibilityQuirk.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@30156 268f45cc-cd09-0410-ab3c-d52691b4dbfc