[cssom] Cleanup around StyleSheet's members

Author: Simon Pieters

cssom/Overview.html

@@ -967,14 +967,13 @@ <h4 id="the-stylesheet-interface"><span class="secno">6.1.1 </span>The <code tit
 
 <p>The <dfn id="dom-stylesheet-type" title="dom-StyleSheet-type"><code>type</code></dfn> attribute must return the <a href="#concept-css-style-sheet-type" title="concept-css-style-sheet-type">type</a>.</p>
 
-<p>The <dfn id="dom-stylesheet-href" title="dom-StyleSheet-href"><code>href</code></dfn> attribute must return the <a href="#concept-css-style-sheet-location" title="concept-css-style-sheet-location">location</a> or null if
-none.</p>
+<p>The <dfn id="dom-stylesheet-href" title="dom-StyleSheet-href"><code>href</code></dfn> attribute must return the <a href="#concept-css-style-sheet-location" title="concept-css-style-sheet-location">location</a>.</p>
 
 <p>The <dfn id="dom-stylesheet-ownernode" title="dom-StyleSheet-ownerNode"><code>ownerNode</code></dfn> attribute must return the <a href="#concept-css-style-sheet-owner-node" title="concept-css-style-sheet-owner-node">owner
-node</a> or null if there is none.</p>
+node</a>.</p>
 
 <p>The <dfn id="dom-stylesheet-parentstylesheet" title="dom-StyleSheet-parentStyleSheet"><code>parentStyleSheet</code></dfn> attribute must return the
-<a href="#concept-css-style-sheet-parent" title="concept-css-style-sheet-parent">parent</a> or null if there is none.</p>
+<a href="#concept-css-style-sheet-parent" title="concept-css-style-sheet-parent">parent</a>.</p>
 
 <p>The <dfn id="dom-stylesheet-title" title="dom-StyleSheet-title"><code>title</code></dfn> attribute must return the <a href="#concept-css-style-sheet-title" title="concept-css-style-sheet-title">title</a> or null if
 <a href="#concept-css-style-sheet-title" title="concept-css-style-sheet-title">title</a> is the empty string.</p>

cssom/Overview.src.html

@@ -898,14 +898,13 @@ <h4>The <code title>StyleSheet</code> Interface</h4>
 
 <p>The <dfn title=dom-StyleSheet-type><code>type</code></dfn> attribute must return the <span title=concept-css-style-sheet-type>type</span>.</p>
 
-<p>The <dfn title=dom-StyleSheet-href><code>href</code></dfn> attribute must return the <span title=concept-css-style-sheet-location>location</span> or null if
-none.</p>
+<p>The <dfn title=dom-StyleSheet-href><code>href</code></dfn> attribute must return the <span title=concept-css-style-sheet-location>location</span>.</p>
 
 <p>The <dfn title=dom-StyleSheet-ownerNode><code>ownerNode</code></dfn> attribute must return the <span title=concept-css-style-sheet-owner-node>owner
-node</span> or null if there is none.</p>
+node</span>.</p>
 
 <p>The <dfn title=dom-StyleSheet-parentStyleSheet><code>parentStyleSheet</code></dfn> attribute must return the
-<span title=concept-css-style-sheet-parent>parent</span> or null if there is none.</p>
+<span title=concept-css-style-sheet-parent>parent</span>.</p>
 
 <p>The <dfn title=dom-StyleSheet-title><code>title</code></dfn> attribute must return the <span title=concept-css-style-sheet-title>title</span> or null if
 <span title=concept-css-style-sheet-title>title</span> is the empty string.</p>