Additional changes:
* Separate CSSCustomProperties.less from skin.less so that
we can obtain the unmodified original values for the colors
Depends-On: I363a97d33d85a9033da753f2a8fe730d80206639
Depends-On: I148eaca747352ffdc9d1423f20d34bd5a1d0e447
Bug: T356427
Change-Id: I916450c276cabb0c7c871525c50f95fb87f498ad