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

third_party/WebKit/Source/core/html/parser/HTMLTreeBuilder.cpp

Index: third_party/WebKit/Source/core/html/parser/HTMLTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/html/parser/HTMLTreeBuilder.cpp b/third_party/WebKit/Source/core/html/parser/HTMLTreeBuilder.cpp
index 7a48396f981a659d1de3d71333f47d2f5d487e36..9fff25be189448ccea757063f7d87ba4bbfe87a5 100644
--- a/third_party/WebKit/Source/core/html/parser/HTMLTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/html/parser/HTMLTreeBuilder.cpp
@@ -480,8 +480,7 @@ static void adjustAttributes(AtomicHTMLToken* token) {
     mapLoweredLocalNameToName(caseMap, attrs.get(), length);
   }
 
-  for (unsigned i = 0; i < token->attributes().size(); ++i) {
-    Attribute& tokenAttribute = token->attributes().at(i);
+  for (auto& tokenAttribute : token->attributes()) {
     const QualifiedName& casedName = caseMap->get(tokenAttribute.localName());
     if (!casedName.localName().isNull())
       tokenAttribute.parserSetName(casedName);