How is Apple suppose to change Firefox and Chrome’s source code?
If either browser’s manufacturer wants to see what Apple does to make Safari more battery efficient, they are free to look at the source code to WebKit.
And as the other person told you already, Safari.app is not what you get if you build the WebKit source. In much the same way that you can't judge Chrome by Chromium, one is the base of the other, not the whole.
