[css-font-loading] Add note about removing SetClass. Fix IDL around promises.

--HG--
extra : rebase_source : 855f21c6be35c810b24d58b5cf069468e81592d6

Author: tabatkins

css-font-loading/Overview.bs

@@ -74,8 +74,8 @@ The <code>FontFace</code> Interface</h2>
 
 			readonly attribute FontFaceLoadStatus status;
 
-			Promise load();
-			attribute Promise loaded;
+			Promise&lt;FontFace> load();
+			attribute Promise&lt;boolean> loaded;
 		};
 	</pre>
 
@@ -297,14 +297,14 @@ The <code>FontFaceSet</code> Interface</h2>
 
 			// check and start loads if appropriate
 			// and fulfill promise when all loads complete
-			Promise load(DOMString font, optional DOMString text = " ");
+			Promise&lt;sequence&lt;FontFace>> load(DOMString font, optional DOMString text = " ");
 
 			// return whether all fonts in the fontlist are loaded
 			// (does not initiate load if not available)
 			boolean check(DOMString font, optional DOMString text = " ");
 
 			// async notification that font loading and layout operations are done
-			Promise ready();
+			Promise&lt;FontFaceSet> ready();
 
 			// loading state, "loading" while one or more fonts loading, "loaded" otherwise
 			readonly attribute FontFaceLoadStatus status;
@@ -313,6 +313,11 @@ The <code>FontFaceSet</code> Interface</h2>
 		FontFaceSet implements EventTarget;
 	</pre>
 
+	Note: The use of [SetClass] is controversial,
+	so this will be rewritten to instead be just a Set look-alike,
+	without use of [SetClass],
+	at least until we figure out how to do this kind of thing correctly.
+
 	The set entries for a <a interface>FontFaceSet</a> is initially an empty list.
 	A <a interface>FontFaceSet</a> attached to a document may have some initial <a interface>FontFace</a> objects prefilled in it;
 	see the section on <a href="#document-font-face-set">Interactions with CSS's @font-face Rule</a> for details.