Add 'creator context security'.

Secure Contexts relied on 'creator Document', which no longer exists. This patch
caches the security status of that Document for the new browsing context's
security checks.

w3c/webappsec-secure-contexts#37

source

@@ -77215,13 +77215,33 @@ dictionary <dfn>DragEventInit</dfn> : <span>MouseEventInit</span> {
   context</span>, then <em>that</em> is its <span>creator browsing context</span>. Otherwise, the
   <span>browsing context</span> has no <span>creator browsing context</span>.</p>
 
-  <p>If a <span>browsing context</span> <var>A</var> has a <span>creator browsing
-  context</span>, then the <dfn>creator origin</dfn>, <dfn>creator URL</dfn>, <dfn>creator base
-  URL</dfn>, and <dfn>creator referrer policy</dfn> are the <span>origin</span>, <span
-  data-x="concept-document-url">URL</span>, <span data-x="document base URL">base URL</span>, and
-  <span data-x="concept-document-referrer-policy">referrer policy</span>, respectively, of the
-  <code>Document</code> that was the <span>active document</span> of that <span>creator browsing
-  context</span> at the time <var>A</var> was created.</p>
+  <p>If a <span>browsing context</span> (<var>context</var>) has a <span>creator browsing
+  context</span> (<var>creator</var>), it also has the following properties whose values are set
+  with regard to <var>creator</var>'s <span>active document</span> at the time <var>context</var>
+  is created (<var>creator document</var>):</p>
+
+  <dl>
+   <dt><dfn>creator origin</dfn></dt>
+   <dd><var>creator document</var>'s <span>origin</span></dd>
+
+   <dt><dfn>creator URL</dfn></dt>
+   <dd><var>creator document</var>'s <span data-x="concept-document-url">URL</span></dd>
+
+   <dt><dfn>creator base URL</dfn></dt>
+   <dd><var>creator document</var>'s <span data-x="document base URL">base URL</span></dd>
+
+   <dt><dfn>creator referrer policy</dfn></dt>
+   <dd>
+    <var>creator document</var>'s <span data-x="concept-document-referrer-policy">referrer
+    policy</span>
+   </dd>
+
+   <dt><dfn>creator context security</dfn></dt>
+   <dd>
+    The result of executing <span>Is <var>environment settings object</var> a Secure
+    Context?</span> on <var>creator document</var>'s <span>relevant settings object</span>
+   </dd>
+  </dl>
 
   <div w-nodev>