Content borders doesn't draw with window styling

[js]

The content border "chrome" (the one set with setContentBorderThickness:forEdge:) is drawn with the default styling, I think it would be nice if the -titleBarDrawingBlock was also also called for content borders

[indragiek]

Interesting idea. I could see how this could be implemented as a separate drawing block, but I don't think it would be wise to use the same -titleBarDrawingBlock to draw the bottom content border as the colors used in the title bar and bottom bar are often different.