Optimistically switch CSSTransformValue to arraylike.

Author: tabatkins

css-typed-om/Overview.bs

@@ -1291,25 +1291,20 @@ They "contain" one or more {{CSSTransformComponent}}s,
 which represent individual <<transform-function>> values.
 
 <xmp class='idl'>
-    [Constructor(optional sequence<CSSTransformComponent> transforms)]
-    interface CSSTransformValue : CSSStyleValue {
-        iterable<CSSTransformComponent>;
-    readonly attribute unsigned long length;
-    getter CSSTransformComponent (unsigned long index);
-        readonly attribute boolean is2D;
-        readonly attribute DOMMatrixReadOnly matrix;
-    };
+[Constructor(optional sequence<CSSTransformComponent> transforms)]
+interface CSSTransformValue : CSSStyleValue {
+    /*arraylike<CSSTransformComponent>;*/
+    readonly attribute boolean is2D;
+    readonly attribute DOMMatrixReadOnly matrix;
+};
 </xmp>
 
+Issue: Assuming the resolution of <a href="https://github.com/heycam/webidl/issues/345">WebIDL#345</a>
+produces an "arraylike" declaration.
+
 A {{CSSTransformValue}}’s [=values to iterate over=]
 is a [=list=] of {{CSSTransformComponent}}s.
 
-The <dfn attribute for=CSSTransformValue>length</dfn> attribute indicates how many {{CSSTransformComponent}} objects
-in the [=values to iterate over=] [=list=].
-
-The <dfn for=CSSTransformValue>indexed getter</dfn> retrieves the {{CSSTransformComponent}} object at the provided index
-from the [=values to iterate over=] [=list=].
-
 <div algorithm>
     The <dfn constructor for=CSSTransformValue>CSSTransformValue(|transforms|)</dfn> constructor must,
     when called,