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

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

Index: third_party/WebKit/Source/core/html/track/AutomaticTrackSelection.cpp
diff --git a/third_party/WebKit/Source/core/html/track/AutomaticTrackSelection.cpp b/third_party/WebKit/Source/core/html/track/AutomaticTrackSelection.cpp
index ef7cc895e724b427d8d0a5b9295df000ac3c072f..651d79063da9e5a10cfdeca8fca508af274bff7a 100644
--- a/third_party/WebKit/Source/core/html/track/AutomaticTrackSelection.cpp
+++ b/third_party/WebKit/Source/core/html/track/AutomaticTrackSelection.cpp
@@ -75,9 +75,7 @@ void AutomaticTrackSelection::performAutomaticTextTrackSelection(
   TextTrack* fallbackTrack = nullptr;
   int highestTrackScore = 0;
 
-  for (size_t i = 0; i < group.tracks.size(); ++i) {
-    TextTrack* textTrack = group.tracks[i];
-
+  for (const auto& textTrack : group.tracks) {
     if (m_configuration.disableCurrentlyEnabledTracks &&
         textTrack->mode() == TextTrack::showingKeyword())
       currentlyEnabledTracks.append(textTrack);
@@ -127,8 +125,7 @@ void AutomaticTrackSelection::performAutomaticTextTrackSelection(
   }
 
   if (currentlyEnabledTracks.size()) {
-    for (size_t i = 0; i < currentlyEnabledTracks.size(); ++i) {
-      TextTrack* textTrack = currentlyEnabledTracks[i];
+    for (const auto& textTrack : currentlyEnabledTracks) {
       if (textTrack != trackToEnable)
         textTrack->setMode(TextTrack::disabledKeyword());
     }