WebKit needs to support real colors with colorspaces
Even if we don't do real color matching on the Mac by default, we should have a Color type which stores ColorSpace information and platforms which want to use that information can.
The plumbing for parts of this are already in place. We would need to add a ColorSpace class to replace the enum which currently exists only on GraphicsContextPrivate. WebCore (principally the CSS system) would need to learn to ask some other object (which knows the current color space) to create colors (possibly the document) instead of just creating them inline. Colors may wish to become RefCounted.
As I mentioned in my comment in GraphicsContextPrivate, there would likely be a shared "pattern colorspace" and "gradient colorspace" which are used to keep track of when GraphicsContext is currently using a gradient or pattern fill/stroke instead of a color-matched solid Color.
Again, all this plumbing could be added w/o turning on color matching support on Mac by default (thus not affecting the PLT speed of Safari).