Add the Priority Hints changes to the fetch spec

fetch.bs

@@ -1733,7 +1733,12 @@ not always relevant and might require different behavior.
 <hr>
 
 <p>A <a for=/>request</a> has an associated
-<dfn export for=request id=concept-request-priority>priority</dfn> (null or a
+<dfn export id=concept-request-priority>priority</dfn>, which is
+"<code>high</code>", "<code>low</code>" or "<code>auto</code>". Unless stated otherwise it is
+"<code>auto</code>".
+
+<p>A <a for=/>request</a> has an associated
+<dfn export for=request id=concept-request-internal-priority>internal priority</dfn> (null or a
 user-agent-defined object). Unless otherwise stated it is null.
 
 <p>A <a for=/>request</a> has an associated
@@ -4133,10 +4138,10 @@ the request.
  <a for=/>header value</a>) to <var>request</var>'s <a for=request>header list</a>.
 
  <li>
-  <p>If <var>request</var>'s <a for=request>priority</a> is null, then use <var>request</var>'s
-  <a for=request>initiator</a>, <a for=request>destination</a>, and
-  <a for=request>render-blocking</a> appropriately in setting <var>request</var>'s
-  <a for=request>priority</a> to a user-agent-defined object.
+  <p>If <var>request</var>'s <a for=request>internal priority</a> is null, then use
+  <var>request</var>'s <a for=request>priority</a>, <a for=request>initiator</a>,
+  <a for=request>destination</a>, and <a for=request>render-blocking</a> appropriately in setting
+  <var>request</var>'s <a for=request>internal priority</a> to a user-agent-defined object.
 
   <p class=note>The user-agent-defined object could encompass stream weight and dependency for
   HTTP/2, and equivalent information used to prioritize dispatch and processing of HTTP/1 fetches.
@@ -6872,6 +6877,7 @@ interface Request {
   readonly attribute boolean isHistoryNavigation;
   readonly attribute AbortSignal signal;
   readonly attribute RequestDuplex duplex;
+  readonly attribute FetchPriority priority;
 
   [NewObject] Request clone();
 };
@@ -6891,6 +6897,7 @@ dictionary RequestInit {
   boolean keepalive;
   AbortSignal? signal;
   RequestDuplex duplex;
+  FetchPriority priority;
   any window; // can only be set to null
 };
 
@@ -6900,6 +6907,7 @@ enum RequestCredentials { "omit", "same-origin", "include" };
 enum RequestCache { "default", "no-store", "reload", "no-cache", "force-cache", "only-if-cached" };
 enum RequestRedirect { "follow", "error", "manual" };
 enum RequestDuplex { "half" };
+enum FetchPriority { "high", "low", "auto" };
 </pre>
 
 <p class="note no-backref">"<code>serviceworker</code>" is omitted from
@@ -6997,6 +7005,9 @@ object), initially null.
    set when {{RequestInit/body}} is a {{ReadableStream}} object. <span class=note>See
    <a href="https://github.com/whatwg/fetch/issues/1254">issue #1254</a> for defining
    "<code>full</code>".</span>
+
+   <dt>{{RequestInit/priority}}
+   <dd>A string to set <var>request</var>'s {{Request/priority}}.
   </dl>
 
  <dt><code><var>request</var> . <a attribute for=Request>method</a></code>
@@ -7070,6 +7081,10 @@ object), initially null.
  <span class=note>See <a href="https://github.com/whatwg/fetch/issues/1254">issue #1254</a> for
  defining "<code>full</code>".</span>
 
+<dt><code><var>request</var> . <a attribute for=Request>priority</a></code>
+ <dd>Returns the <a>priority</a> of the <var>request</var>, e.g., "<code>high</code>",
+ "<code>low</code>" or "<code>auto</code>".
+
  <dt><code><var>request</var> . <a method for=Request>clone</a>()</code>
  <dd><p>Returns a clone of <var>request</var>.
 </dl>
@@ -7184,6 +7199,9 @@ constructor steps are:
    <dt><a for=request>priority</a>
    <dd><var>request</var>'s <a for=request>priority</a>.
 
+   <dt><a for=request>internal priority</a>
+   <dd><var>request</var>'s <a for=request>internal priority</a>.
+
    <dt><a for=request>origin</a>
    <dd><var>request</var>'s <a for=request>origin</a>. <span class=note>The propagation of the
    <a for=/>origin</a> is only significant for navigation requests being handled by a service
@@ -8431,6 +8449,7 @@ Odin Hørthe Omdal,
 Olli Pettay,
 Ondřej Žára,
 O. Opsec,
+Patrick Meenan,
 Perry Jiang<!-- perryjiang; Github -->,
 Philip Jägenstedt,
 R. Auburn,