[css-typed-om] algorithm for coercing value should specify parseMultiple flag

[dbaron]

The spec describes an algorithm that coerces value into an appropriate type for a given property.

It says:

Parse a CSSStyleValue with property property and value value and return the resulting value.

I think it should also say that the parseMultiple flag should be true. And it should describe the value as a cssText, so I think it should instead say something more like:

Parse a CSSStyleValue with property property, cssText value, and parseMultiple true, and return the resulting value.

[tabatkins]

Fixed.