应该是和color range功能重合被砍了，原来有个luma key也不见了
adobe的ae cc官方新特性说明（ http://blogs.adobe.com/aftereffects/2013/09/after-effects-cc-12-1-whats-new-and-changed.html ）写到：
The Color Key effect and Luma Key effect are now in the Obsolete category. (In most cases, you should be using superior effects such as Keylight and the Extract effect.)
所以应该是从key里面移到obsolete里了（手机回复，未验证）
