Remove OTIFICATION_METRIC_EVENT_DURATION that no-one is observing

chrome/browser/metrics/metric_event_duration_details.h

Index: chrome/browser/metrics/metric_event_duration_details.h
diff --git a/chrome/browser/metrics/metric_event_duration_details.h b/chrome/browser/metrics/metric_event_duration_details.h
deleted file mode 100644
index 3e2feec7a06e7bb5877eb9aace0aa2a26743c3d4..0000000000000000000000000000000000000000
--- a/chrome/browser/metrics/metric_event_duration_details.h
+++ /dev/null
@@ -1,20 +0,0 @@
-// Copyright (c) 2009 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.
-
-#ifndef CHROME_BROWSER_METRICS_METRIC_EVENT_DURATION_DETAILS_H_
-#define CHROME_BROWSER_METRICS_METRIC_EVENT_DURATION_DETAILS_H_
-
-#include <string>
-
-// Used when sending a notification about an event that occurred that we want
-// to time.
-struct MetricEventDurationDetails {
-  MetricEventDurationDetails(const std::string& e, int d)
-      : event_name(e), duration_ms(d) {}
-
-  std::string event_name;
-  int duration_ms;
-};
-
-#endif  // CHROME_BROWSER_METRICS_METRIC_EVENT_DURATION_DETAILS_H_