Stop requiring an event loop for queue a microtask

A microtask cannot cross the event loop boundary and thus necessarily has a surrounding agent. As such the event loop is always clear (but the document might not be).

Without this you would get weird results in at least two cases:

* A microtask would never run if it were queued on an event loop without tasks.
* A microtask queued on another event loop could interleave microtasks on the currently running task of that event loop.

Author: annevk

source

@@ -105762,8 +105762,7 @@ dictionary <dfn dictionary>PromiseRejectionEventInit</dfn> : <span>EventInit</sp
    </li>
 
    <li>
-    <p><span>Queue a microtask</span> on the <span>surrounding agent</span>'s <span
-    data-x="concept-agent-event-loop">event loop</span> to perform the following steps:</p>
+    <p><span>Queue a microtask</span> to perform the following steps:</p>
 
     <ol>
      <li><p>If <var>job settings</var> is not null, then <span>check if we can run script</span>
@@ -106444,11 +106443,14 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
   </ol>
 
   <p>To <dfn export>queue a microtask</dfn> which performs a series of steps <var>steps</var>,
-  optionally given an event loop <var>event loop</var> and a document <var>document</var>:</p>
+  optionally given a document <var>document</var>:</p>
 
   <ol>
-   <li><p>If <var>event loop</var> was not given, set <var>event loop</var> to the <span>implied
-   event loop</span>.</p></li>
+   <li><p><span>Assert</span>: there is a <span>surrounding agent</span>. I.e., this algorithm is
+   not called while <span>in parallel</span>.</p></li>
+
+   <li><p>Let <var>eventLoop</var> be the <span>surrounding agent</span>'s <span
+   data-x="concept-agent-event-loop">event loop</span>.</p></li>
 
    <li><p>If <var>document</var> was not given, set <var>document</var> to the <span>implied
    document</span>.</p></li>
@@ -106467,7 +106469,7 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
    <li><p>Set <var>microtask</var>'s <span>script evaluation environment settings object set</span>
    to an empty <span>set</span>.</p></li>
 
-   <li><p><span>Enqueue</span> <var>microtask</var> on <var>event loop</var>'s <span>microtask
+   <li><p><span>Enqueue</span> <var>microtask</var> on <var>eventLoop</var>'s <span>microtask
    queue</span>.</p></li>
   </ol>
 
@@ -106484,8 +106486,7 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
   exception is algorithms involving or specifying cross-agent communication (e.g., between a window
   and a worker); for those cases, the <span>implied event loop</span> concept must not be relied
   upon and specifications must explicitly provide an <span>event loop</span> when <span
-  data-x="queue a task">queuing a task</span> or <span data-x="queue a
-  microtask">microtask</span>.</p>
+  data-x="queue a task">queuing a task</span>.</p>
 
   <p>The <dfn>implied document</dfn> when queuing a task on an <span>event loop</span> <var>event
   loop</var> is determined as follows:</p>