Add issue about removing the fallback behavior from image-set().

Author: tabatkins

css4-images/Overview.html

@@ -874,6 +874,14 @@ <h3 id=image-set-notation><span class=secno>4.3. </span> Resolution
    dimensions</i></a>; otherwise, the function represents an <a
    href="#invalid-image"><i>invalid image</i></a>.
 
+  <p class=issue> It's been suggested that we don't need the fallback
+   behavior here, and should instead just choose one resource and stick with
+   it, allowing authors to next image() if they want to do fallback. That's
+   not strictly the same, and it's more verbose, but it may be enough. If we
+   remove the fallback behavior, we can probably kill the &lt;color> as well,
+   unless we think it's important to avoid the verbosity of a wrapping
+   ‘<code class=css>image(image-set(...), blue)</code>’.
+
   <p> If an <a href="#image-set-decl-type"><i>&lt;image-set-decl></i></a> is
    chosen and successfully loaded, the associated <a
    href="#resolution-type"><i>&lt;resolution></i></a> is the image's <a

css4-images/Overview.src.html

@@ -584,6 +584,17 @@ <h3 id='image-set-notation'>
 		the function represents a solid-color image of the given color with no <i>intrinsic dimensions</i>;
 		otherwise, the function represents an <i>invalid image</i>.
 
+	<p class='issue'>
+		It's been suggested that we don't need the fallback behavior here,
+		and should instead just choose one resource and stick with it,
+		allowing authors to next image() if they want to do fallback.
+		That's not strictly the same,
+		and it's more verbose,
+		but it may be enough.
+		If we remove the fallback behavior,
+		we can probably kill the &lt;color> as well,
+		unless we think it's important to avoid the verbosity of a wrapping ''image(image-set(...), blue)''.
+
 	<p>
 		If an <i>&lt;image-set-decl></i> is chosen and successfully loaded,
 		the associated <i>&lt;resolution></i> is the image's <i>intrinsic resolution</i>.