Editorial: add some <div algorithm> wrappers

And improve the algorithm "headers" at the same time by listing the argument types and default values.

dom.bs

@@ -6264,8 +6264,9 @@ steps:
 
 <hr>
 
+<div algorithm>
 <p>To <dfn export id=concept-element-attributes-get-by-name>get an attribute by name</dfn> given a
-<var>qualifiedName</var> and <a for=/>element</a> <var>element</var>, run these steps:
+string <var>qualifiedName</var> and an <a for=/>element</a> <var>element</var>:
 
 <ol>
  <li><p>If <var>element</var> is in the <a>HTML namespace</a> and its <a for=Node>node document</a>
@@ -6275,11 +6276,13 @@ steps:
  <li><p>Return the first <a>attribute</a> in <var>element</var>'s <a for=Element>attribute list</a>
  whose <a for=Attr>qualified name</a> is <var>qualifiedName</var>; otherwise null.
 </ol>
+</div>
 
+<div algorithm>
 <p>To
 <dfn export id=concept-element-attributes-get-by-namespace>get an attribute by namespace and local name</dfn>
-given a <var>namespace</var>, <var>localName</var>, and <a for=/>element</a> <var>element</var>,
-run these steps:
+given null or a string <var>namespace</var>, a string <var>localName</var>, and an
+<a for=/>element</a> <var>element</var>:
 
 <ol>
  <li><p>If <var>namespace</var> is the empty string, then set it to null.
@@ -6288,10 +6291,12 @@ run these steps:
  <a for=Attr>namespace</a> is <var>namespace</var> and <a for=Attr>local name</a> is
  <var>localName</var>, if any; otherwise null.
 </ol>
+</div>
 
+<div algorithm>
 <p>To <dfn export id=concept-element-attributes-get-value>get an attribute value</dfn> given an
-<a for=/>element</a> <var>element</var>, <var>localName</var>, and optionally a <var>namespace</var>
-(null unless stated otherwise), run these steps:</p>
+<a for=/>element</a> <var>element</var>, a string <var>localName</var>, and an optional null or
+string <var>namespace</var> (default null):</p>
 
 <ol>
  <li><p>Let <var>attr</var> be the result of
@@ -6302,9 +6307,11 @@ run these steps:
 
  <li><p>Return <var>attr</var>'s <a for=Attr>value</a>.</p></li>
 </ol>
+</div>
 
+<div algorithm>
 <p>To <dfn export id=concept-element-attributes-set>set an attribute</dfn> given an
-<var>attr</var> and <var>element</var>, run these steps:
+<a for=/>attribute</a> <var>attr</var> and an <a for=/>element</a> <var>element</var>:
 
 <ol>
  <li><p>If <var>attr</var>'s <a for=Attr>element</a> is neither null nor <var>element</var>,
@@ -6324,16 +6331,15 @@ run these steps:
 
  <li><p>Return <var>oldAttr</var>.
 </ol>
+</div>
 
-<p>To <dfn export id=concept-element-attributes-set-value>set an attribute value</dfn> for an
-<a for=/>element</a> <var>element</var>, using a <var>localName</var> and <var>value</var>, and an
-optional <var>prefix</var>, and <var>namespace</var>, run these steps:
+<div algorithm>
+<p>To <dfn export id=concept-element-attributes-set-value>set an attribute value</dfn> given an
+<a for=/>element</a> <var>element</var>, a string <var>localName</var>, a string <var>value</var>,
+an optional null or string <var>prefix</var> (default null), and an optional null or string
+<var>namespace</var> (default null):
 
 <ol>
- <li>If <var>prefix</var> is not given, set it to null.
-
- <li>If <var>namespace</var> is not given, set it to null.
-
  <li>Let <var>attribute</var> be the result of
  <a lt="get an attribute by namespace and local name">getting an attribute</a> given
  <var>namespace</var>, <var>localName</var>, and <var>element</var>.
@@ -6347,9 +6353,11 @@ optional <var>prefix</var>, and <var>namespace</var>, run these steps:
 
  <li><p><a lt="change an attribute">Change</a> <var>attribute</var> to <var>value</var>.
 </ol>
+</div>
 
+<div algorithm>
 <p>To <dfn export id=concept-element-attributes-remove-by-name>remove an attribute by name</dfn>
-given a <var>qualifiedName</var> and <a for=/>element</a> <var>element</var>, run these steps:
+given a string <var>qualifiedName</var> and an <a for=/>element</a> <var>element</var>:
 
 <ol>
  <li><p>Let <var>attr</var> be the result of
@@ -6360,11 +6368,13 @@ given a <var>qualifiedName</var> and <a for=/>element</a> <var>element</var>, ru
 
  <li><p>Return <var>attr</var>.
 </ol>
+</div>
 
+<div algorithm>
 <p>To
 <dfn export id=concept-element-attributes-remove-by-namespace>remove an attribute by namespace and local name</dfn>
-given a <var>namespace</var>, <var>localName</var>, and <a for=/>element</a> <var>element</var>,
-run these steps:
+given null or a string <var>namespace</var>, a string <var>localName</var>, and an
+<a for=/>element</a> <var>element</var>:
 
 <ol>
  <li><p>Let <var>attr</var> be the result of
@@ -6375,6 +6385,7 @@ run these steps:
 
  <li><p>Return <var>attr</var>.
 </ol>
+</div>
 
 <hr>