Add abort reason to abort fetch

fetch.bs

@@ -231,6 +231,9 @@ lt="authentication entry">authentication entries</a> (for HTTP authentication).
 
  <dt><dfn for="fetch controller">report timing steps</dfn> (default null)
  <dd>Null or an algorithm accepting a <a for=/>global object</a>.
+
+ <dt><dfn for="fetch controller">serialized abort reason</dfn> (default null)
+ <dd>Null or a serialization from [$StructuredSerialize$].
 </dl>
 
 <p>To <dfn export for="fetch controller" id="finalize-and-report-timing">report timing</dfn> for a
@@ -254,8 +257,20 @@ given a <a>fetch controller</a> <var>controller</var>:
 </ol>
 
 <p>To <dfn export for="fetch controller">abort</dfn> a <a for=/>fetch controller</a>
-<var>controller</var>, set <var>controller</var>'s <a for="fetch controller">state</a> to
-"<code>aborted</code>".
+<var>controller</var> with optional <var>error</var>:
+
+<ol>
+ <li><p>Set <var>controller</var>'s <a for="fetch controller">state</a> to "<code>aborted</code>".
+
+ <li><p>Let <var>error</var> be an "{{AbortError}}" {{DOMException}}, if it is not given.
+
+ <li><p>Let <var>serializedError</var> be [$StructuredSerialize$](<var>error</var>).
+ If that threw an exception, catch it, and let <var>serializedError</var> be
+ [$StructuredSerialize$](a new "{{AbortError}}" {{DOMException}}).
+
+ <li><p>Set <var>controller</var>'s <a for="fetch controller">serialized abort reason</a> to
+ <var>serializedError</var>.
+</ol>
 
 <p>To <dfn export for="fetch controller">terminate</dfn> a <a for=/>fetch controller</a>
 <var>controller</var>, set <var>controller</var>'s <a for="fetch controller">state</a> to
@@ -5654,7 +5669,8 @@ optional boolean <var>forceNewConnection</var> (default false), run these steps:
  ongoing fetch if it is <a lt=suspend for=fetch>suspended</a>.
 
  <li><p>Let <var>cancelAlgorithm</var> be an algorithm that <a for="fetch controller">aborts</a>
- <var>fetchParams</var>'s <a for="fetch params">controller</a>.
+ <var>fetchParams</var>'s <a for="fetch params">controller</a> with <var>reason</var>, given
+ <var>reason</var>.
 
  <li><p>Let <var>highWaterMark</var> be a non-negative, non-NaN number, chosen by the user agent.
 
@@ -7740,7 +7756,8 @@ method steps are:
   then:
 
   <ol>
-   <li><p><a>Abort fetch</a> with <var>p</var>, <var>request</var>, and null.
+   <li><p><a>Abort the fetch() call</a> with <var>p</var>, <var>request</var>, null, and <var>requestObject</var>'s
+   <a for=Request>signal</a>'s <a for=AbortSignal>abort reason</a>.
 
    <li><p>Return <var>p</var>.
   </ol>
@@ -7770,10 +7787,12 @@ method steps are:
   <ol>
    <li><p>Set <var>locallyAborted</var> to true.
 
-   <li><p><a>Abort fetch</a> with <var>p</var>, <var>request</var>, and <var>responseObject</var>.
+   <li><p><a>Abort the fetch() call</a> with <var>p</var>, <var>request</var>, <var>responseObject</var>, and
+   <var>requestObject</var>'s <a for=Request>signal</a>'s <a for=AbortSignal>abort reason</a>.
 
    <li><p>If <var>controller</var> is not null, then <a for="fetch controller">abort</a>
-   <var>controller</var>.
+   <var>controller</var> with <var>requestObject</var>'s <a for=Request>signal</a>'s
+   <a for=AbortSignal>abort reason</a>.
   </ol>
 
  <li>
@@ -7784,9 +7803,21 @@ method steps are:
   <ol>
    <li><p>If <var>locallyAborted</var> is true, terminate these substeps.
 
-   <li><p>If <var>response</var>'s <a for=response>aborted flag</a> is set, then <a>abort fetch</a>
-   with <var>p</var>, <var>request</var>, and <var>responseObject</var>, and terminate these
-   substeps.
+   <li><p>If <var>response</var>'s <a for=response>aborted flag</a> is set, then:
+
+   <ol>
+    <li><p>Let <var>error</var> be an "{{AbortError}}" {{DOMException}}.
+
+    <li><p>If <var>requestObject</var>'s <a for=Request>signal</a>'s <a for=AbortSignal>abort reason</a>
+    is not undefined, set <var>error</var> to <var>requestObject</var>'s <a for=Request>signal</a>'s
+    <a for=AbortSignal>abort reason</a>.
+
+    <li><p><a>Abort the fetch() call</a> with <var>p</var>, <var>request</var>, <var>responseObject</var>, and
+    <var>error</var>.
+
+    <li><p><a for="fetch controller">Abort</a> <var>controller</var> with <var>error</var>, and
+    terminate these substeps.
+   </ol>
 
    <li><p>If <var>response</var> is a <a>network error</a>, then <a for=/>reject</a> <var>p</var>
    with a {{TypeError}} and terminate these substeps.
@@ -7800,12 +7831,10 @@ method steps are:
  <li><p>Return <var>p</var>.
 </ol>
 
-<p>To <dfn>abort fetch</dfn> with a <var>promise</var>, <var>request</var>, and
-<var>responseObject</var>, run these steps:
+<p>To <dfn lt="abort the fetch() call" export id=abort-fetch-algorithm>abort a fetch() call</dfn> with a
+<var>promise</var>, <var>request</var>, <var>responseObject</var>, and an <var>error</var>, run these steps:
 
 <ol>
- <li><p>Let <var>error</var> be an "<code><a exception>AbortError</a></code>" {{DOMException}}.
-
  <li>
   <p><a for=/>Reject</a> <var>promise</var> with <var>error</var>.
 
@@ -8411,6 +8440,7 @@ Moritz Kneilmann,
 Ms2ger,
 Nico Schlömer,
 Nicolás Peña Moreno,
+Nidhi Jaju,
 Nikhil Marathe,
 Nikki Bee,
 Nikunj Mehta,