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

Source/core/html/track/CueTimeline.cpp

Index: Source/core/html/track/CueTimeline.cpp
diff --git a/Source/core/html/track/CueTimeline.cpp b/Source/core/html/track/CueTimeline.cpp
index 5d27c78ea2a530ff0085ad181fa71dbc6607342e..6c1d7e3dd6f19c1aa9b8af95f042d9e559bd24e6 100644
--- a/Source/core/html/track/CueTimeline.cpp
+++ b/Source/core/html/track/CueTimeline.cpp
@@ -132,6 +132,8 @@ void CueTimeline::updateActiveCues(double movieTime)
 
     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