Avoid WTF::Vector::at() and operator[] in core/html.

third_party/WebKit/Source/core/html/track/TextTrackContainer.cpp

 /*
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 91 matching lines @@
   // Note: Removing all children will cause them to be re-inserted below,
   // invalidating the layout.
   // effect
   if (reset)
     removeChildren();
 
   // 10. For each text track cue cue in cues that has not yet had
   // corresponding CSS boxes added to output, in text track cue order, run the
   // following substeps:
   double movieTime = video.currentTime();
-  for (size_t i = 0; i < activeCues.size(); ++i) {
-    TextTrackCue* cue = activeCues[i].data();
+  for (const auto& activeCue : activeCues) {
+    TextTrackCue* cue = activeCue.data();
 
     DCHECK(cue->isActive());
     if (!cue->track() || !cue->track()->isRendered() || !cue->isActive())
       continue;
 
     cue->updateDisplay(*this);
     cue->updatePastAndFutureNodes(movieTime);
   }
 
   // 11. Return output.
   // See the note for step 3 for why there is no output to return.
 }
 
 }  // namespace blink