Introduce the possiblity to expose microphone/camera state via MediaS…

…treamTrack muted state.

In that case, mention that action handlers are first called, then mute/unmute events fire.

index.bs

@@ -82,6 +82,11 @@ urlPrefix: https://www.w3.org/TR/permissions-policy-1/; spec: PermissionsPolicy
 urlPrefix: https://html.spec.whatwg.org/multipage/dom.html; spec: dom
     type: dfn
         text: permissions policy; url:#concept-document-permissions-policy
+urlPrefix: https://www.w3.org/TR/mediacapture-streams/; spec: mediacapture-main
+    type: dfn
+        text: MediaStreamTrack; url:#mediastreamtrack
+        text: MediaStreamTrack muted state; url:#track-muted
+        text: set MediaStreamTrack muted state; url:#set-track-muted
 </pre>
 
 <h2 id="introduction">Introduction</h2>
@@ -587,6 +592,15 @@ conforming IDL fragments, as described in the Web IDL specification. [[!WEBIDL]]
       for=MediaSessionAction>hangup</a> <a>media session actions</a> if none was
       provided for the <a>active media session</a>.
     </p>
+    <p>
+      A user agent MAY expose microphone and camera state to web pages via <a>
+      MediaStreamTrack muted state</a>. In the case of a <a enum-value
+      for=MediaSessionAction>togglemicrophone</a> or <a enum-value
+      for=MediaSessionAction>togglecamera</a> <a>media session action</a>, user
+      agent MUST first execute the corresponding {{MediaSessionActionHandler}},
+      and then execute the steps to <a>set MediaStreamTrack muted state</a> for
+      each related <a>MediaStreamTrack</a>.
+    </p>
 
     <p class=note>
       A page should only register a {{MediaSessionActionHandler}} for a <a>media