Move skinClass settings from default skins for components like scrollbars and sliders from being hardcoded in MXML to CSS

My understanding is that there are some default CSS stylesheets that get applied to Flex components.

Instead of hardcoding skinClass'es for things like tracks and thumbs in the default skins for scrollbars and sliders and such, why not move the declarations of the skinClass to the default CSS stylesheets.

This would prevent us from having to create replacement skins for the sliders and scrollbars just to change the skins on tracks and thumbs, because without the replacements skins, we cannot override the skinClass settings.

See the recipe I added today for such a procedure:
http://cookbooks.adobe.com/post_How_do_you_customize_the_thumb_appearance_on_a_Spa-16231.html