WTF/std normalization: replace WTF::Vector::first() with ::front()

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

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 220 matching lines @@
     transientRegistrations[i]->clearTransientRegistrations();
 
   if (m_records.isEmpty())
     return;
 
   MutationRecordVector records;
   records.swap(m_records);
 
   // Report the first (earliest) stack as the async cause.
   InspectorInstrumentation::AsyncTask asyncTask(
-      m_callback->getExecutionContext(), records.first());
+      m_callback->getExecutionContext(), records.front());
   m_callback->call(records, this);
 }
 
 void MutationObserver::resumeSuspendedObservers() {
   DCHECK(isMainThread());
   if (suspendedMutationObservers().isEmpty())
     return;
 
   MutationObserverVector suspended;
   copyToVector(suspendedMutationObservers(), suspended);
@@ skipping 20 matching lines @@
 }
 
 DEFINE_TRACE(MutationObserver) {
   visitor->trace(m_callback);
   visitor->trace(m_records);
   visitor->trace(m_registrations);
   visitor->trace(m_callback);
 }
 
 }  // namespace blink