Use container::back() and container::pop_back() in ui/

ui/events/ozone/evdev/libgestures_glue/gesture_logging.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/ozone/evdev/libgestures_glue/gesture_logging.h"
 
 #include <gestures/gestures.h>
 #include <stdarg.h>
 
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 
 namespace {
 
 std::string FormatLog(const char* fmt, va_list args) {
   std::string msg = base::StringPrintV(fmt, args);
-  if (!msg.empty() && msg[msg.size() - 1] == '\n')
-    msg.erase(msg.end() - 1, msg.end());
+  if (!msg.empty() && msg.back() == '\n')
+    msg.pop_back();
   return msg;
 }
 
 }  // namespace
 
 void gestures_log(int verb, const char* fmt, ...) {
   va_list args;
   va_start(args, fmt);
   if (verb <= GESTURES_LOG_ERROR)
     LOG(ERROR) << "gestures: " << FormatLog(fmt, args);
   else if (verb <= GESTURES_LOG_INFO)
     VLOG(3) << "gestures: " << FormatLog(fmt, args);
   va_end(args);
 }