Document calls to the "rules for updating the text track rendering"

Source/core/html/track/CueTimeline.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/html/track/CueTimeline.h"
 
 #include "core/events/Event.h"
 #include "core/html/HTMLMediaElement.h"
 #include "core/html/HTMLTrackElement.h"
@@ skipping 114 matching lines @@
     // 4.8.10.8 Playing the media resource
 
     //  If the current playback position changes while the steps are running,
     //  then the user agent must wait for the steps to complete, and then must
     //  immediately rerun the steps.
     if (ignoreUpdateRequests())
         return;
 
     HTMLMediaElement& mediaElement = this->mediaElement();
 
+    // https://html.spec.whatwg.org/#time-marches-on
+
     // 1 - Let current cues be a list of cues, initialized to contain all the
     // cues of all the hidden, showing, or showing by default text tracks of the
     // media element (not the disabled ones) whose start times are less than or
     // equal to the current playback position and whose end times are greater
     // than the current playback position.
     CueList currentCues;
 
     // The user agent must synchronously unset [the text track cue active] flag
     // whenever ... the media element's readyState is changed back to HAVE_NOTHING.
     if (mediaElement.readyState() != HTMLMediaElement::HAVE_NOTHING && mediaElement.webMediaPlayer())
@@ skipping 200 matching lines @@
     if (!m_ignoreUpdate && mediaElement().inActiveDocument())
         updateActiveCues(mediaElement().currentTime());
 }
 
 DEFINE_TRACE(CueTimeline)
 {
     visitor->trace(m_mediaElement);
 }
 
 } // namespace blink