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

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

Index: third_party/WebKit/Source/core/dom/StyleEngine.cpp
diff --git a/third_party/WebKit/Source/core/dom/StyleEngine.cpp b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
index d707d0d2e4e046919580a86a6645da23eb19b8cc..c34438007902b7978798d93f15501be8bc43cfc5 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngine.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
@@ -559,8 +559,8 @@ void StyleEngine::removeFontFaceRules(
     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();
 }