Add text about local sources and remove early return on non-local sou…

…rce in MediaStreamTrack.stop()

getusermedia.html

@@ -545,7 +545,11 @@ <h2>MediaStream</h2>
     <section>
       <h2>MediaStreamTrack</h2>
       <p>A <code><a>MediaStreamTrack</a></code> object represents a media
-      source in the User Agent. Several <code><a>MediaStreamTrack</a></code>
+      source in the User Agent. A source, unless stated otherwise, is a
+      <dfn>local source</dfn> representing a device connected to the User
+      Agent. Other specifications may define sources for <code>
+      <a>MediaStreamTrack</a></code> that override the behavior specified here.
+      Several <code><a>MediaStreamTrack</a></code>
       objects can represent the same media source, e.g., when the user chooses
       the same camera in the UI shown by two consecutive calls to
       <code><a>getUserMedia()</a></code> .</p>
@@ -881,14 +885,11 @@ <h3>Interface Definition</h3>
                 <p>Let <var>track</var> be the current
                 <code><a>MediaStreamTrack</a></code> object.</p>
               </li>
-              <li>
-                <p>If <var>track</var> is sourced by a non-local source, then
-                abort these steps.</p>
-              </li>
               <li>
                 <p>Notify <var>track</var>'s source that <var>track</var> is
-                <a href="#track-ended">ended</a> so that the source may be
-                <a href="#source-stopped">stopped</a>, unless other
+                <a href="#track-ended">ended</a>.</p>
+                <p>A <a>local source</a> that is notified of a track ending
+                will be <a href="#source-stopped">stopped</a>, unless other
                 <code><a>MediaStreamTrack</a></code> objects depend on it.</p>
               </li>
               <li>