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

third_party/WebKit/Source/core/events/ScopedEventQueue.cpp

Index: third_party/WebKit/Source/core/events/ScopedEventQueue.cpp
diff --git a/third_party/WebKit/Source/core/events/ScopedEventQueue.cpp b/third_party/WebKit/Source/core/events/ScopedEventQueue.cpp
index 4d54982ce6af48273eb68959d54300fd64fb4e47..3fdd596b51c2c4d2f99641ae888b9a549d03e6db 100644
--- a/third_party/WebKit/Source/core/events/ScopedEventQueue.cpp
+++ b/third_party/WebKit/Source/core/events/ScopedEventQueue.cpp
@@ -66,8 +66,8 @@ void ScopedEventQueue::dispatchAllEvents() {
   HeapVector<Member<EventDispatchMediator>> queuedEventDispatchMediators;
   queuedEventDispatchMediators.swap(m_queuedEventDispatchMediators);
 
-  for (size_t i = 0; i < queuedEventDispatchMediators.size(); i++)
-    dispatchEvent(queuedEventDispatchMediators[i].release());
+  for (auto& mediator : queuedEventDispatchMediators)
+    dispatchEvent(mediator.release());
 }
 
 void ScopedEventQueue::dispatchEvent(EventDispatchMediator* mediator) const {