Use current instead of incumbent + entry in worker constructors

As shown by https://settings-object-worker-client-abibrisfdk.now.sh, all
browsers use the current settings object for the fetch client, i.e. the
"outside settings", instead of the incumbent settings object. (Except we
do not know the result in Edge, since they don't seem to send a Referer
header for us to inspect.) Part of #1430.

As shown by
https://settings-object-worker-client-wellwosyqf.now.sh/entry/entry.html,
all browsers also use the current settings object for URL resolution,
instead of the entry settings object. Part of #1431.

source

@@ -87187,18 +87187,19 @@ interface <dfn>NavigatorOnLine</dfn> {
  <pre>&lt;!DOCTYPE html>
 &lt;iframe>&lt;/iframe>
 &lt;script>
- new frames[0].Worker('worker.js');
+ new frames[0].MessageChannel();
 &lt;/script></pre>
 
- <p>When the <code data-x="dom-Worker">Worker()</code> constructor looks up the <span>incumbent
- settings object</span> to use for various parts of its algorithm, the <span>topmost script-having
- execution context</span> will be that corresponding to the <code>script</code> element: it was
- pushed onto the <span>JavaScript execution context stack</span> as part of <span
- data-x="js-ScriptEvaluation">ScriptEvaluation</span> during the <span>run a classic script</span>
- algorithm. Since there are no Web IDL callback invocations involved, the context's
- <span>skip-when-determining-incumbent counter</span> is zero, so it is used to determine the
- <span>incumbent settings object</span>; the result is the <span>environment settings
- object</span> of <code data-x="">window</code>.</p>
+ <p>When the <code data-x="dom-MessageChannel">MessageChannel()</code> constructor looks up the
+ <span>incumbent settings object</span> to use as the <span
+ data-x="concept-port-owner">owner</span> of the new <code>MessagePort</code> objects, the
+ <span>topmost script-having execution context</span> will be that corresponding to the
+ <code>script</code> element: it was pushed onto the <span>JavaScript execution context
+ stack</span> as part of <span data-x="js-ScriptEvaluation">ScriptEvaluation</span> during the
+ <span>run a classic script</span> algorithm. Since there are no Web IDL callback invocations
+ involved, the context's <span>skip-when-determining-incumbent counter</span> is zero, so it is
+ used to determine the <span>incumbent settings object</span>; the result is the <span>environment
+ settings object</span> of <code data-x="">window</code>.</p>
 
  <p>(In this example, the <span>environment settings object</span> of <code
  data-x="">frames[0]</code> is not involved at all. It is the <span>current settings
@@ -96799,8 +96800,10 @@ enum <dfn>WorkerType</dfn> { "classic", "module" };
  <code>DOMException</code> and abort these steps if the request violates a policy decision (e.g.
  if the user agent is configured to not allow the page to start dedicated workers).</p></li>
 
- <li><p><span data-x="parse a url">Parse</span> the <var>scriptURL</var> argument relative to the
- <span>entry settings object</span>.</p></li>
+ <li><p>Let <var>outside settings</var> be the <span>current settings object</span>.</p>
+
+ <li><p><span data-x="parse a url">Parse</span> the <var>scriptURL</var> argument relative to
+ <var>outside settings</var>.</p></li>
 
  <li><p>If this fails, throw a <span>"<code>SyntaxError</code>"</span> <code>DOMException</code>
  and abort these steps.</p></li>
@@ -96812,8 +96815,6 @@ enum <dfn>WorkerType</dfn> { "classic", "module" };
  data-x="blob protocol">blob:</code> URLs.</p>
  </li>
 
- <li><p>Let <var>outside settings</var> be the <span>incumbent settings object</span>.</p>
-
  <li><p>Let <var>worker</var> be a new <code>Worker</code> object.</p></li>
 
  <li><p><span>Create a new <code>MessagePort</code> object</span> whose <span
@@ -96874,8 +96875,10 @@ interface <dfn>SharedWorker</dfn> : <span>EventTarget</span> {
  <code>DOMException</code> and abort these steps if the request violates a policy decision (e.g.
  if the user agent is configured to not allow the page to start shared workers).</p></li>
 
- <li><p><span data-x="parse a url">Parse</span> <var>scriptURL</var> relative to the <span>entry
- settings object</span>.</p></li>
+ <li><p>Let <var>outside settings</var> be the <span>current settings object</span>.</p></li>
+
+ <li><p><span data-x="parse a url">Parse</span> <var>scriptURL</var> relative to <var>outside
+ settings</var>.</p></li>
 
  <li><p>If this fails, throw a <span>"<code>SyntaxError</code>"</span> <code>DOMException</code>
  and abort these steps.</p></li>
@@ -96888,8 +96891,6 @@ interface <dfn>SharedWorker</dfn> : <span>EventTarget</span> {
  data-x="blob protocol">blob:</code> URLs.</p>
  </li>
 
- <li><p>Let <var>outside settings</var> be the <span>incumbent settings object</span>.</p></li>
-
  <li>
 
  <p>Execute the following substeps atomically:</p>