Implement UMA log throttling for cellular connections

components/metrics/metrics_pref_names.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 "components/metrics/metrics_pref_names.h"
 
 namespace metrics {
 namespace prefs {
 
 // Set once, to the current epoch time, on the first run of chrome on this
@@ skipping 151 matching lines @@
     "user_experience_metrics.stability.stats_version";
 
 // The keys below are strictly increasing counters over the lifetime of
 // a chrome installation. They are (optionally) sent up to the uninstall
 // survey in the event of uninstallation.
 const char kUninstallLaunchCount[] = "uninstall_metrics.launch_count";
 const char kUninstallMetricsPageLoadCount[] =
     "uninstall_metrics.page_load_count";
 const char kUninstallMetricsUptimeSec[] = "uninstall_metrics.uptime_sec";
 
+// TODO
+const char kUserCellDataUse[] = "user_call_datause";
+const char kUmaCellDataUse[] = "uma_call_datause";
 }  // namespace prefs
 }  // namespace metrics