Define how cross-origin isolated impacts BCGs

BCGs being browsing context groups.

Author: annevk

source

@@ -89471,31 +89471,35 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
   ensure that web developers see interoperable behavior with regard to shared memory, even in the
   face of varying and changing user agent process models.</p>
 
+  <p>An <span>agent cluster</span> has an associated <dfn>cross-origin isolated</dfn> (a boolean),
+  which is initially false.</p>
+  <!-- TODO: maybe this should move into the eventual COEP PR as it impacts shared workers? -->
+
+
   <div w-nodev>
 
   <hr>
 
   <p>The following defines the allocation of the <span data-x="agent cluster">agent clusters</span>
   of <span data-x="similar-origin window agent">similar-origin window agents</span>.</p>
 
-  <p>An <dfn>agent cluster key</dfn> is a <span>site</span>.</p>
-
-  <p class="XXX"><a href="https://github.com/whatwg/html/pull/4734">whatwg/html #4734</a> is
-  expected to widen <span>agent cluster key</span> (but not <span>site</span>) to encompass all
-  <span data-x="concept-origin-tuple">tuple origins</span>.</p>
-
-  <p>To <dfn data-x="obtain-agent-cluster-key">obtain an agent cluster key</dfn>, given an origin
-  <var>origin</var>, return the result of <span data-x="obtain a site">obtaining a site</span> with
-  <var>origin</var>.</p>
+  <p>An <dfn>agent cluster key</dfn> is a <span>site</span> or <span
+  data-x="concept-origin-tuple">tuple origin</span> whose <span
+  data-x="concept-origin-host">host</span>'s <span>registrable domain</span> is non-null. I.e., an
+  <span>agent cluster key</span> can be any <span>origin</span>.</p>
 
   <p>To <dfn data-x="obtain-similar-origin-window-agent">obtain a similar-origin window agent</dfn>,
   given an <span>origin</span> <var>origin</var> and <span>browsing context group</span>
   <var>group</var>, run these steps:</p>
 
   <ol>
-   <li><p>Let <var>clusterKey</var> be the result of <span
-   data-x="obtain-agent-cluster-key" data-export="">obtaining an agent cluster key</span> given
-   <var>origin</var>.</p></li>
+   <li><p>Let <var>clusterKey</var> be the result of <span data-x="obtain a site">obtaining a
+   site</span> with <var>origin</var>.</p></li>
+
+   <li><p>If <var>group</var>'s <dfn data-x="bcg cross-origin isolated">cross-origin isolated</dfn>
+   is true, then set <var>clusterKey</var> to <var>origin</var>.</p></li>
+   <!-- TODO: this is not the place to <dfn> this, but doing this for now so the build does not
+        fail. https://github.com/whatwg/html/pull/5334 will take care of this.  -->
 
    <li><p>Let <var>agentCluster</var> be the result of <span
    data-x="obtain-browsing-agent-cluster">obtaining a browsing context agent cluster</span> with
@@ -89508,14 +89512,21 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
   <p>To <dfn data-x="obtain-browsing-agent-cluster">obtain a browsing context agent cluster</dfn>,
   given a <span>browsing context group</span> <var>group</var> and <span>agent cluster key</span>
   <var>key</var>, run these steps:</p>
+  <!-- Question: why not fold this into the above algorithm? Does it really need to be separate?
+       Might even add some clarity around the return value of the above algorithm. -->
 
   <ol>
    <li>
     <p>If <var>group</var>'s <span>agent cluster map</span>[<var>key</var>] <span data-x="map
     exists">does not exist, then:</span></p>
+
     <ol>
      <li><p>Let <var>agentCluster</var> be a new <span>agent cluster</span>.</p></li>
 
+     <li><p>If <var>group</var>'s <span data-x="bcg cross-origin isolated">cross-origin
+     isolated</span> is true, then set <var>agentCluster</var>'s <span>cross-origin isolated</span>
+     to true.</p></li>
+
      <li><p>Add the result of <span data-x="create an agent">creating an agent</span>, given false,
      to <var>agentCluster</var>.</p></li>