[css-shapes] Accept percentage for shape-image-threshold

[BorisChiou]

The current spec of shape-image-threshold uses <number> as its value. However, it seems this property is also kind of alpha value, and #3342 suggests we add <percentage> for opacity related properties. Therefore, I just wonder should we update shape-image-threshold to accept <alpha-value>?

cc @ericwilligers @emilio

[ewilligers]

No objections.

[css-meeting-bot]

The CSS Working Group just discussed Accept percentage for shape-image-threshold, and agreed to the following:

• RESOLVED: Treat shape-image-threshold as an opacity prop and allow %

The full IRC log of that discussion

<dael> Topic: Accept percentage for shape-image-threshold
<dael> github: https://github.com//issues/4102
<dael> emilio: Recently gecko added alpha value syntax. shape-image-threshold takes an alpha makes sense
<dael> astearns: Makes sense to me. Any concerns?
<dael> astearns: Prop: Treat shape-image-threshold as an opacity prop and allow %
<dael> RESOLVED: Treat shape-image-threshold as an opacity prop and allow %