Define contentDocument using a more clearly defined shared concept

PR: #1181

source

@@ -28231,11 +28231,9 @@ href="?audio">audio&lt;/a> test instead.)&lt;/p></pre>
   must <span>reflect</span> the <code data-x="attr-iframe-referrerpolicy">referrerpolicy</code>
   content attribute, <span>limited to only known values</span>.</p>
 
-  <p>The <dfn><code data-x="dom-iframe-contentDocument">contentDocument</code></dfn> IDL attribute
-  must return the <code>Document</code> object of the <span>active document</span> of the
-  <code>iframe</code> element's <span>nested browsing context</span>, if any and if its
-  <span>origin</span> is the <span>same origin-domain</span> as the <span>origin</span> specified by
-  the <span>incumbent settings object</span>, or null otherwise.</p>
+  <p>The <dfn><code data-x="dom-iframe-contentDocument">contentDocument</code></dfn> IDL attribute,
+  on getting, must return the <code>iframe</code> element's <span
+  data-x="concept-bcc-content-document">content document</span>.</p>
 
   <p>The <dfn><code data-x="dom-iframe-contentWindow">contentWindow</code></dfn> IDL attribute must
   return the <code>WindowProxy</code> object of the <code>iframe</code> element's <span>nested
@@ -29376,11 +29374,9 @@ attribute, set the <span>browsing context name</span> of the element's <span>nes
   attribute. The <dfn><code data-x="dom-object-useMap">useMap</code></dfn> IDL attribute must
   <span>reflect</span> the <code data-x="attr-hyperlink-usemap">usemap</code> content attribute.</p>
 
-  <p>The <dfn><code data-x="dom-object-contentDocument">contentDocument</code></dfn> IDL attribute
-  must return the <code>Document</code> object of the <span>active document</span> of the
-  <code>object</code> element's <span>nested browsing context</span>, if any and if its
-  <span>origin</span> is the <span>same origin-domain</span> as the <span>origin</span> specified by
-  the <span>incumbent settings object</span>, or null otherwise.</p>
+  <p>The <dfn><code data-x="dom-object-contentDocument">contentDocument</code></dfn> IDL attribute,
+  on getting, must return the <code>object</code> element's <span
+  data-x="concept-bcc-content-document">content document</span>.</p>
 
   <p>The <dfn><code data-x="dom-object-contentWindow">contentWindow</code></dfn> IDL attribute must
   return the <code>WindowProxy</code> object of the <code>object</code> element's <span>nested
@@ -76967,6 +76963,25 @@ dictionary <dfn>DragEventInit</dfn> : <span>MouseEventInit</span> {
   <span data-x="browsing context">browsing contexts</span> that are <span data-x="browsing context
   nested through">nested through</span> the <code>Document</code> object.</p>
 
+  <p>The <dfn data-x="concept-bcc-content-document">content document</dfn> of a <span>browsing
+  context container</span> <var>container</var> is the result of the following algorithm:</p>
+
+  <ol>
+   <li><p>If <var>container</var> does not have a <span>nested browsing context</span>, then return
+   null.</p></li>
+
+   <li><p>Let <var>context</var> be <var>container</var>'s <span>nested browsing
+   context</span>.</p></li>
+
+   <li><p>Let <var>document</var> be <var>context</var>'s <span>active document</span>.</p></li>
+
+   <li><p>If <var>document</var>'s <span>origin</span> and the <span>origin</span> specified by the
+   <span>incumbent settings object</span> are not <span>same origin-domain</span>, then return
+   null.</p></li>
+
+   <li><p>Return <var>document</var>.</p></li>
+  </ol>
+
 
   <h5>Navigating nested browsing contexts in the DOM</h5>
 
@@ -111807,11 +111822,9 @@ if (s = prompt('What is your name?')) {
   <code>frame</code> element must <span>reflect</span> the element's <code
   undefined data-x="attr-frame-noresize">noresize</code> content attribute.</p>
 
-  <p>The <dfn><code data-x="dom-frame-contentDocument">contentDocument</code></dfn> IDL attribute of
-  the <code>frame</code> element must return the <code>Document</code> object of the <span>active
-  document</span> of the <code>frame</code> element's <span>nested browsing context</span>, if any
-  and if its <span>origin</span> is the <span>same origin-domain</span> as the <span>origin</span>
-  specified by the <span>incumbent settings object</span>, or null otherwise.</p>
+  <p>The <dfn><code data-x="dom-frame-contentDocument">contentDocument</code></dfn> IDL attribute,
+  on getting, must return the <code>frame</code> element's <span
+  data-x="concept-bcc-content-document">content document</span>.</p>
 
   <p>The <dfn><code data-x="dom-frame-contentWindow">contentWindow</code></dfn> IDL attribute must
   return the <code>WindowProxy</code> object of the <code>frame</code> element's <span>nested