Add clarification on ended as well as mute

getusermedia.html

@@ -847,13 +847,17 @@ <h4>Life-cycle</h4>
         <p>If all {{MediaStreamTrack}}s that are using the same
         source are [= track/ended =], the source will be
         [= source/stopped =].</p>
-        <p>When a {{MediaStreamTrack}} object ends for any
-        reason (e.g., because the user rescinds the permission for the page to
-        use the local camera, or because the application invoked the
-        {{MediaStreamTrack/stop()}} method on
-        the {{MediaStreamTrack}} object, or because the User
-        Agent has instructed the track to end for any reason) it is said to be
+        <p>When the application has invoked the {{MediaStreamTrack/stop()}}
+        method on a {{MediaStreamTrack}} object, or when the [=source=] of a
+        {{MediaStreamTrack}} ends production of live samples to its tracks,
+        whichever is sooner, a {{MediaStreamTrack}} is said to be
         <dfn id="track-ended" data-dfn-for="track" data-export>ended</dfn>.</p>
+        <p>For camera and microphone sources, the reasons for a source to end
+        [=ended|end=] its tracks for reasons other than
+        {{MediaStreamTrack/stop()}} are [=implementation-defined=]
+        (e.g., because the user rescinds the permission for the page to
+        use the local camera, or because the User
+        Agent has instructed the track to end for any reason).</p>
         <p>When a {{MediaStreamTrack}} <var>track</var>
         <dfn data-lt="track ended by the User agent" data-for=MediaStreamTrack data-export id="ends-nostop">ends for any reason other than the {{MediaStreamTrack/stop()}} method being
         invoked</dfn>, the [=User Agent=] MUST queue a task that runs the following
@@ -899,14 +903,15 @@ <h4>Media Flow</h4>
         muted, and enabled / disabled.</p>
         <p><dfn data-export id=
         "track-muted">Muted</dfn> refers to the input to the
-        {{MediaStreamTrack}}. If live samples are not made
-        available to the {{MediaStreamTrack}} it is muted.</p>
+        {{MediaStreamTrack}}. Live samples MUST NOT be made available to a
+        {{MediaStreamTrack}} while it is [=muted=].</p>
         <p>{{Muted}} is outside the control of web applications, but can be observed by
         the application by reading the {{MediaStreamTrack/muted}} attribute and listening
         to the associated events {{mute}} and {{unmute}}. The reasons for a
         {{MediaStreamTrack}} to be muted are defined by its <a>source</a>.</p>
-        <p>For camera and microphone sources, there can be
-        several reasons for a {{MediaStreamTrack}} to be muted:
+        <p>For camera and microphone sources, the reasons to [=muted|mute=] are
+        [=implementation-defined=]. This allows user agents to implement privacy
+        mitigations in situations like:
         the user pushing a physical mute button on the microphone, the user
         closing a laptop lid with an embedded camera, the user toggling a
         control in the operating system, the user clicking a mute button in the
@@ -917,9 +922,13 @@ <h4>Media Flow</h4>
         this information to the web application through {{MediaStreamTrack/muted}} and
         its associated events.</p>
 
-        <p>Whenever the [=User Agent=] initiates such a change, it MUST queue a
+        <p>Whenever the [=User Agent=] initiates such an [= implementation-defined=]
+        change for camera or microphone sources, it MUST queue a
         task, using the user interaction task source, to [=set a track's muted
         state=] to the state desired by the user.</p>
+        <div class="note">This does not apply to [=source|sources=] defined in
+        other specifications. Other specifications need to define their own steps
+        to [=set a track's muted state=] if desired.</div>
         <p>To <dfn class="abstract-op" id="set-track-muted">set a track's muted state</dfn> to
         <var>newState</var>, the [=User Agent=] MUST run the following steps:</p>
         <ol class="algorithm">