Fix for width of section views getting out of whack

When using auto layout the previous code would have an issue on 10.8 in if the palette was used inside an NSTabView. The subviews using auto layout constraints would not get updated properly.

This fix removes a previous workaround and reduces it to the actually necessary updating of the content view bounds. The subview frames are getting updated by the autoresizing masks or the layout constraints that are getting created from these.