[css-values] Move empty URL section out of the way of normal readers. Add to changes list. Update DoC

Author: fantasai

css-values/Overview.bs

@@ -539,19 +539,6 @@ Resource Locators: the <<url>> type</h3>
 	(If written as a normal function containing a string, ordinary string escaping rules apply;
 		only newlines and the character used to quote the string need to be escaped.)
 
-	If the value of the ''url()'' is the empty string
-	(like ''url("")'' or ''url()''),
-	the url must resolve to an invalid resource
-	(similar to what the url ''about:invalid'' does).
-
-	Note: This matches the behavior of empty urls for embedded resources elsewhere in the web platform,
-	and avoids excess traffic re-requesting the stylesheet or host document
-	due to editting mistakes leaving the ''url()'' value empty,
-	which are almost certain to be invalid resources for whatever the ''url()'' shows up in.
-	Linking on the web platform <em>does</em> allow empty urls,
-	so if/when CSS gains some functionality to control hyperlinks,
-	this restriction can be relaxed in those contexts.
-
 <h4 id="relative-urls">
 Relative URLs</h4>
 
@@ -631,6 +618,22 @@ Fragment URLs</h4>
 		regardless of what its URL is.
 	</details>
 
+<h4 id="url-empty">
+Empty URLs</h4>
+
+	If the value of the ''url()'' is the empty string
+	(like ''url("")'' or ''url()''),
+	the url must resolve to an invalid resource
+	(similar to what the url ''about:invalid'' does).
+
+	Note: This matches the behavior of empty urls for embedded resources elsewhere in the web platform,
+	and avoids excess traffic re-requesting the stylesheet or host document
+	due to editting mistakes leaving the ''url()'' value empty,
+	which are almost certain to be invalid resources for whatever the ''url()'' shows up in.
+	Linking on the web platform <em>does</em> allow empty urls,
+	so if/when CSS gains some functionality to control hyperlinks,
+	this restriction can be relaxed in those contexts.
+
 <h4 id='url-modifiers'>
 URL Modifiers</h4>
 
@@ -2183,6 +2186,8 @@ Changes</h2>
 	<ul>
 		<li>Allow zero angles to be represented as ''0''.
 		    (Change due to Web-compatibility constraints in transform and gradient syntaxes.)
+		<li>Defined an empty <<url>> resolves to an invalid resource.
+
 	</ul>
 
 	Changes since the <a href="https://www.w3.org/TR/2013/CR-css3-values-20130730/">30 July 2013 Candidate Recommendation</a> are:

css-values/issues-cr-2015.bsi

@@ -156,3 +156,16 @@ Response: https://lists.w3.org/Archives/Public/www-style/2016Mar/0178.html
 Closed:   Accepted
 Resolved:
 ----
+Issue 19.
+Summary:  pushState() breaks relative URL resolution
+From:     Tab Atkins
+Comment:  https://lists.w3.org/Archives/Public/www-style/2016Mar/0298.html
+Open:     Edits need review
+Resolved: https://lists.w3.org/Archives/Public/www-style/2016May/0209.html
+----
+Issue 20.
+Summary:  Define case-sensitivity of attr()
+From:     Simon Pieters
+Comment:  https://lists.w3.org/Archives/Public/www-style/2016Apr/0067.html
+Open
+----