Make --enable-benchmarking not affect metrics recording.

components/metrics/metrics_switches.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_switches.h"
 
 namespace metrics {
 namespace switches {
 
+// Enables the recording of metrics reports but disables reporting. In contrast
+// to kDisableMetrics, this executes all the code that a normal client would
+// use for reporting, except the report is dropped rather than sent to the
+// server. This is useful for finding issues in the metrics code during UI and
+// performance tests.
+const char kMetricsRecordingOnly[] = "metrics-recording-only";
+
 // Forces a reset of the one-time-randomized FieldTrials on this client, also
 // known as the Chrome Variations state.
 const char kResetVariationState[] = "reset-variation-state";
 
 }  // namespace switches
 }  // namespace metrics