Remove EventPath::at(), which is redundant

EventPath: :operator[] can be used.
Change-Id: I97a49e26c2903e7966d23594e8283e77b5bd235d
Reviewed-on: https://chromium-review.googlesource.com/c/1333170Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607500}

third_party/blink/renderer/core/dom/events/event_path.cc

@@ -306,7 +306,7 @@ bool ShouldStopEventPath(EventTarget& adjusted_target,
 void EventPath::ShrinkForRelatedTarget(const Node& event_target_node,
                                        const Node& event_related_target_node) {
   for (wtf_size_t i = 0; i < size(); ++i) {
-    if (ShouldStopEventPath(*at(i).Target(), *at(i).RelatedTarget(),
+    if (ShouldStopEventPath(*(*this)[i].Target(), *(*this)[i].RelatedTarget(),
                             event_target_node, event_related_target_node)) {
       Shrink(i);
       break;

third_party/blink/renderer/core/dom/events/event_path.h

@@ -62,7 +62,6 @@ class CORE_EXPORT EventPath final
   const NodeEventContext& operator[](wtf_size_t index) const {
     return node_event_contexts_[index];
   }
-  NodeEventContext& at(wtf_size_t index) { return node_event_contexts_[index]; }
   NodeEventContext& Last() { return node_event_contexts_[size() - 1]; }
 
   WindowEventContext& GetWindowEventContext() {