Clean up some code change

talk/app/webrtc/fakemetricsobserver.cc

 /*
  * libjingle
  * Copyright 2015 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 18 matching lines @@
 #include "webrtc/base/checks.h"
 
 namespace webrtc {
 
 FakeMetricsObserver::FakeMetricsObserver() {
   Reset();
 }
 
 void FakeMetricsObserver::Reset() {
   DCHECK(thread_checker_.CalledOnValidThread());
-  counters_ = std::vector<std::vector<int>>();
+  counters_.clear();
   memset(int_histogram_samples_, 0, sizeof(int_histogram_samples_));
   for (std::string& type : string_histogram_samples_) {
     type.clear();
   }
 }
 
 void FakeMetricsObserver::IncrementEnumCounter(
     PeerConnectionEnumCounterType type,
     int counter,
     int counter_max) {
@@ skipping 35 matching lines @@
   return int_histogram_samples_[type];
 }
 
 const std::string& FakeMetricsObserver::GetStringHistogramSample(
     PeerConnectionMetricsName type) const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return string_histogram_samples_[type];
 }
 
 }  // namespace webrtc