[csswg-drafts] Pull Request: [cssom] Don't serialize shorthand if importance differs

upsuper has just labeled a pull request from upsuper for 
https://github.com/w3c/csswg-drafts as "cssom-1":

== [cssom] Don't serialize shorthand if importance differs ==
For the following declarations:
```css
div {
  background: green;
  background-image: none !important;
}
```
the current spec should return something for 
`getPropertyValue('background')`, but all browsers (even Servo) agree 
on that this should return nothing because the importance of its 
longhands differ.

This PR fixes this issue.

It can alternatively be fixed in "serialize a CSS value" algorithm. 
Given that the other callsite of this algorithm with a list (which is 
"serialize a CSS declaration block") already handles important flag 
itself, I guess it is better being put in `getPropertyValue` rather 
than "serialize a CSS value".

See https://github.com/w3c/csswg-drafts/pull/870

Received on Monday, 9 January 2017 03:34:37 UTC