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

third_party/WebKit/Source/core/dom/StyleEngine.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 541 matching lines @@
     m_resolver->invalidateMatchedPropertiesCache();
   FontCache::fontCache()->invalidateShapeCache();
 }
 
 void StyleEngine::removeFontFaceRules(
     const HeapVector<Member<const StyleRuleFontFace>>& fontFaceRules) {
   if (!m_fontSelector)
     return;
 
   FontFaceCache* cache = m_fontSelector->fontFaceCache();
-  for (unsigned i = 0; i < fontFaceRules.size(); ++i)
-    cache->remove(fontFaceRules[i]);
+  for (const auto& rule : fontFaceRules)
+    cache->remove(rule);
   if (m_resolver)
     m_resolver->invalidateMatchedPropertiesCache();
 }
 
 void StyleEngine::markTreeScopeDirty(TreeScope& scope) {
   if (scope == m_document) {
     markDocumentDirty();
     return;
   }
 
@@ skipping 667 matching lines @@
 }
 
 DEFINE_TRACE_WRAPPERS(StyleEngine) {
   for (auto sheet : m_injectedAuthorStyleSheets) {
     visitor->traceWrappers(sheet);
   }
   visitor->traceWrappers(m_documentStyleSheetCollection);
 }
 
 }  // namespace blink