Merge pull request #177 from zcorpan/fix-166

Fix #166

index.bs

@@ -657,10 +657,23 @@ Parsing a <code>srcset</code> Attribute</h4>
 			<a>Collect a sequence of characters</a> that are not
 			<a>space characters</a>, and let that be <var>url</var>.
 
+		<li>
+			Let <var>descriptors</var> be the empty string.
+
 		<li>
 			If <var>url</var> ends with a U+002C COMMA character
-			(,), remove that character from <var>url</var> and let
-			<var>descriptors</var> be the empty string. Otherwise,
+			(,), follow these substeps:
+
+			<ol>
+				<li>
+					Remove all trailing U+002C COMMA characters from <var>url</var>.
+
+				<li>
+					If <var>url</var> is empty, then jump to
+					the step labeled <i title>splitting loop</i>.
+			</ol>
+
+			Otherwise,
 			follow these substeps:
 
 			<ol>
@@ -670,10 +683,26 @@ Parsing a <code>srcset</code> Attribute</h4>
 					parser</i>.
 
 				<li>
+					<i title>Descriptor collection loop</i>:
 					<a>Collect a sequence of characters</a>
 					that are not U+002C COMMA characters
-					(,), and let that be
-					<var>descriptors</var>.
+					(,) or U+0028 LEFT PARENTHESIS ((),
+					and append the result to <var>descriptors</var>.
+
+				<li>
+					If the character at <var>position</var> is a U+002C COMMA character,
+					jump to the step labeled <i title>skip comma</i>.
+
+				<li>
+					<a>Collect a sequence of characters</a> that are not
+					U+0029 RIGHT PARENTHESIS ()) and append the result to <var>descriptors</var>.
+
+				<li>
+					Jump to the step labeled <i title>descriptor collection loop</i>.
+
+				<li>
+					<i title>Skip comma</i>: Advance <var>position</var> to the next character in
+					<var>input</var>.
 			</ol>
 
 		<li>
@@ -685,11 +714,6 @@ Parsing a <code>srcset</code> Attribute</h4>
 			<var>input</var>, then jump to the step labeled
 			<i title>descriptor parser</i>.
 
-		<li>
-			Advance <var>position</var> to the next character in
-			<var>input</var> (skipping past the U+002C COMMA
-			character (,) separating this candidate from the next).
-
 		<li>
 			Return to the step labeled <i title>splitting loop</i>.