It makes the following WPT tests pass:
- css/css-color/predefined-001.html
- css/css-color/xyz-003.html
- css/css-color/xyz-d50-003.html
- css/css-color/xyz-d50-004.html
- css/css-color/xyz-d65-003.html
Also we now render the reference of color-mix-currentcolor-nested-for-
color-property.html properly. Which means that it's now different from
the actual test, that is still rendered incorrectly. In other word, the
false positive for this test is now turned into a true negative.
