[css-values-3] Drop unitless <<angle>> per WG resolution. https://lists.w3.org/Archives/Public/www-style/2017Apr/0027.html

Author: fantasai

css-values-3/Overview.bs

@@ -1194,8 +1194,6 @@ Other Quantities</h2>
 Angle Units: the <<angle>> type and ''deg'', ''grad'', ''rad'', ''turn'' units</h3>
 
 	Angle values are <<dimension>>s denoted by <dfn id="angle-value">&lt;angle></dfn>.
-	However, for zero angles the unit identifier is optional
-	(i.e. can be syntactically represented as the <a>number</a> ''0'').
 	The angle unit identifiers are:
 
 	<dl export dfn-type=value dfn-for="<angle>">
@@ -1236,6 +1234,11 @@ Angle Units: the <<angle>> type and ''deg'', ''grad'', ''rad'', ''turn'' units</
 		is interpreted as a bearing angle.
 	</div>
 
+	Note: For legacy reasons,
+	some uses of <<angle>> allow a bare ''0'' to mean ''0deg''.
+	This is not true in general, however,
+	and will not occur in future uses of the <<angle>> type.
+
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@@ -1594,7 +1597,7 @@ Type Checking</h4>
 	An ''attr()'' expression's type is given by its <<type-or-unit>> argument.
 
 	Note: Because <<number-token>>s are always interpreted as <<number>>s or <<integer>>s,
-	"unitless 0" <<length>>s or <<angle>>s aren't supported in ''calc()''.
+	"unitless 0" <<length>>s aren't supported in ''calc()''.
 	That is, ''width: calc(0 + 5px);'' is invalid,
 	even though both ''width: 0;''
 	and ''width: 5px;''

css-values-3/issues-cr-2016.bsi

@@ -98,3 +98,10 @@ From:     fantasai
 Comment:  https://github.com/w3c/csswg-drafts/issues/708#issuecomment-302240095
 Open:     =WG= Discuss.
 -----
+Issue 14.
+Summary:  Restrict unitless 0 for angles to specific functions that need it
+From:     Tab Atkins
+Comment:  https://lists.w3.org/Archives/Public/www-style/2017Apr/0027.html
+Closed:   Accepted
+Resolved: https://lists.w3.org/Archives/Public/www-style/2017Apr/0027.html
+----

css-values-3/issues-cr-2016.html

@@ -133,6 +133,13 @@ <h1>CSS Values and Units Level 3 Disposition of Comments for 2016-09-29 CR</h1>
 <span>Comment:  <a href='https://github.com/w3c/csswg-drafts/issues/708#issuecomment-302240095'>https://github.com/w3c/csswg-drafts/issues/708#issuecomment-302240095</a></span>
 <span class="">Open:     =WG= Discuss.</span>
 <span>-</span></pre>
+<pre class=' a' id='issue-14'>
+<span>Issue 14. <a href='#issue-14'>#</a></span>
+<span>Summary:  Restrict unitless 0 for angles to specific functions that need it</span>
+<span>From:     Tab Atkins</span>
+<span>Comment:  <a href='https://lists.w3.org/Archives/Public/www-style/2017Apr/0027.html'>https://lists.w3.org/Archives/Public/www-style/2017Apr/0027.html</a> <a href="https://www.w3.org/Mail/flatten/index?subject=https%3A%2F%2Flists.w3.org%2FArchives%2FPublic%2Fwww-style/2017Apr/0027.html"><abbr title="Thread">&#x2208;</abbr></a></span>
+<span class="a">Closed:   Accepted</span>
+<span>Resolved: <a href='https://lists.w3.org/Archives/Public/www-style/2017Apr/0027.html'>https://lists.w3.org/Archives/Public/www-style/2017Apr/0027.html</a> <a href="https://www.w3.org/Mail/flatten/index?subject=https%3A%2F%2Flists.w3.org%2FArchives%2FPublic%2Fwww-style/2017Apr/0027.html"><abbr title="Thread">&#x2208;</abbr></a></span></pre>
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