Define that the CSSNumberish attributes on transform components rectify on set (so they're always CSSUnitValues). Fixes #611.

Author: tabatkins

css-typed-om/Overview.bs

@@ -2191,6 +2191,13 @@ The <dfn for=CSSTransformValue>indexed getter</dfn> retrieves the transform comp
         and its {{CSSTransformComponent/is2D}} internal slot set to `false`.
 </div>
 
+<div algorithm="CSSRotate.x" dfn-type=attribute dfn-for=CSSRotate>
+    The <dfn>x</dfn>, <dfn>y</dfn>, and <dfn>z</dfn> attributes must,
+    on setting to a new value |val|,
+    [=rectify a numberish value=] from |val|
+    and set the corresponding internal slot to the result of that.
+</div>
+
 <div algorithm="CSSScale()">
     The <dfn constructor for=CSSScale>CSSScale(|x|, |y|, |z|)</dfn> constructor must,
     when invoked,
@@ -2219,6 +2226,13 @@ The <dfn for=CSSTransformValue>indexed getter</dfn> retrieves the transform comp
     6. Return |this|.
 </div>
 
+<div algorithm="CSSScale.x" dfn-type=attribute dfn-for=CSSScale>
+    The <dfn>x</dfn>, <dfn>y</dfn>, and <dfn>z</dfn> attributes must,
+    on setting to a new value |val|,
+    [=rectify a numberish value=] from |val|
+    and set the corresponding internal slot to the result of that.
+</div>
+
 <div algorithm="CSSSkew()">
     The <dfn constructor for=CSSSkew>CSSSkew(|ax|, |ay|)</dfn> constructor must,
     when invoked,