Sync the documentation of seekable() with the MediaSource specification

Source/modules/mediasource/MediaSource.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 349 matching lines @@
 
     return intersectionRanges.release();
 }
 
 PassRefPtrWillBeRawPtr<TimeRanges> MediaSource::seekable() const
 {
     // Implements MediaSource algorithm for HTMLMediaElement.seekable.
     // https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html#htmlmediaelement-extensions
 
     double sourceDuration = duration();
-    // 1. If duration equals NaN then return an empty TimeRanges object.
+    // If duration equals NaN: Return an empty TimeRanges object.
     if (std::isnan(sourceDuration))
         return TimeRanges::create();
 
-    // 2. If duration equals positive Infinity, then return a single range with a start time of 0 and an end time equal to the
-    // highest end time reported by the HTMLMediaElement.buffered attribute.
+    // If duration equals positive Infinity:
     if (sourceDuration == std::numeric_limits<double>::infinity()) {
         RefPtrWillBeRawPtr<TimeRanges> buffered = m_attachedElement->buffered();
+
+        // 1. If the HTMLMediaElement.buffered attribute returns an empty TimeRanges object, then
+        // return an empty TimeRanges object and abort these steps.
         if (buffered->length() == 0)
             return TimeRanges::create();
+
+        // 2. Return a single range with a start time of 0 and an end time equal to the highest end
+        // time reported by the HTMLMediaElement.buffered attribute.
         return TimeRanges::create(0, buffered->end(buffered->length() - 1, ASSERT_NO_EXCEPTION));
     }
 
-    // 3. Otherwise, return a single range with a start time of 0 and an end time equal to duration.
+    // 3. Otherwise: Return a single range with a start time of 0 and an end time equal to duration.
     return TimeRanges::create(0, sourceDuration);
 }
 
 void MediaSource::setDuration(double duration, ExceptionState& exceptionState)
 {
     // 2.1 http://www.w3.org/TR/media-source/#widl-MediaSource-duration
     // 1. If the value being set is negative or NaN then throw an InvalidAccessError
     // exception and abort these steps.
     if (std::isnan(duration)) {
         exceptionState.throwDOMException(InvalidAccessError, ExceptionMessages::notAFiniteNumber(duration, "duration"));
@@ skipping 214 matching lines @@
 
     m_asyncEventQueue->enqueueEvent(event.release());
 }
 
 URLRegistry& MediaSource::registry() const
 {
     return MediaSourceRegistry::registry();
 }
 
 } // namespace blink