Add TODO to remove page_load_histograms.h/.cc

chrome/renderer/page_load_histograms.cc

 // Copyright (c) 2012 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.
 
+// TODO(bmcquade): delete this class in October 2016, as it is deprecated by the
+// new PageLoad.* UMA histograms.
+
 #include "chrome/renderer/page_load_histograms.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
@@ skipping 616 matching lines @@
   Time start = document_state->start_load_time();
   Time finish = document_state->finish_load_time();
   // TODO(mbelshe): should we log more stats?
   VLOG(1) << "PLT: " << (finish - start).InMilliseconds() << "ms "
           << url.spec();
 }
 
 void PageLoadHistograms::OnDestruct() {
   delete this;
 }