Introduce a target browsing context concept for MIX and CSP

Overview.html

@@ -553,9 +553,7 @@ <h4 id="requests"><span class="secno">3.1.5 </span>Requests</h4>
 
 <p>A <a href="#concept-request" title="concept-request">request</a> has an associated
 <dfn id="concept-request-client" title="concept-request-client">client</dfn> (null or an
-<a class="external" data-anolis-spec="html" href="https://html.spec.whatwg.org/multipage/webappapis.html#environment-settings-object">environment settings object</a>). <span class="note">It is
-null when <a class="external" data-anolis-spec="html" href="https://html.spec.whatwg.org/multipage/browsers.html#navigate" title="navigate">navigating</a>, service worker
-script updates, etc.</span>
+<a class="external" data-anolis-spec="html" href="https://html.spec.whatwg.org/multipage/webappapis.html#environment-settings-object">environment settings object</a>).
 
 <p>A <a href="#concept-request" title="concept-request">request</a> has an associated
 <dfn id="concept-request-window" title="concept-request-window">window</dfn> ("<code>no-window</code>",
@@ -572,6 +570,10 @@ <h4 id="requests"><span class="secno">3.1.5 </span>Requests</h4>
 not have to explicitly set <a href="#concept-request" title="concept-request">request</a>'s
 <a href="#concept-request-window" title="concept-request-window">window</a>.
 
+<p>A <a href="#concept-request" title="concept-request">request</a> has an associated
+<dfn id="concept-request-target-browsing-context" title="concept-request-target-browsing-context">target browsing context</dfn> (null or a
+<a class="external" data-anolis-spec="html" href="https://html.spec.whatwg.org/multipage/browsers.html#browsing-context">browsing context</a>). Unless stated otherwise it is null.
+
 <p>A <a href="#concept-request" title="concept-request">request</a> has an associated
 <dfn id="keep-alive-flag">keep-alive flag</dfn>. Unless stated otherwise it is unset.
 

Overview.src.html

@@ -498,9 +498,7 @@ <h4>Requests</h4>
 
 <p>A <span title=concept-request>request</span> has an associated
 <dfn title=concept-request-client>client</dfn> (null or an
-<span data-anolis-spec=html>environment settings object</span>). <span class=note>It is
-null when <span data-anolis-spec=html title=navigate>navigating</span>, service worker
-script updates, etc.</span>
+<span data-anolis-spec=html>environment settings object</span>).
 
 <p>A <span title=concept-request>request</span> has an associated
 <dfn title=concept-request-window>window</dfn> ("<code>no-window</code>",
@@ -517,6 +515,10 @@ <h4>Requests</h4>
 not have to explicitly set <span title=concept-request>request</span>'s
 <span title=concept-request-window>window</span>.
 
+<p>A <span title=concept-request>request</span> has an associated
+<dfn title=concept-request-target-browsing-context>target browsing context</dfn> (null or a
+<span data-anolis-spec=html>browsing context</span>). Unless stated otherwise it is null.
+
 <p>A <span title=concept-request>request</span> has an associated
 <dfn>keep-alive flag</dfn>. Unless stated otherwise it is unset.