Measure how often the users are encountering MD5...

net/base/connection_type_histograms.cc

+// Copyright (c) 2008 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 "net/base/connection_type_histograms.h"
+
+#include "base/histogram.h"
+
+namespace net {
+
+// We're using a histogram as a group of counters.  We're only interested in
+// the values of the counters.  Ignore the shape, average, and standard
+// deviation of the histograms because they are meaningless.
+//
+// We use two groups of counters.  In the first group (counter1), each counter
+// is a boolean (0 or 1) that indicates whether the user has seen a connection
+// of that type during that session.  In the second group (counter2), each
+// counter is the number of connections of that type the user has seen during
+// that session.
+void UpdateConnectionTypeHistograms(ConnectionType type) {
+  static bool had_connection_type[NUM_OF_CONNECTION_TYPES];
+  static LinearHistogram counter1(L"Net.HadConnectionType",
+                                  1, NUM_OF_CONNECTION_TYPES - 1,
+                                  NUM_OF_CONNECTION_TYPES);
+  static LinearHistogram counter2(L"Net.ConnectionTypeCount",
+                                  1, NUM_OF_CONNECTION_TYPES - 1,
+                                  NUM_OF_CONNECTION_TYPES);
+
+  if (type >= 0 && type < NUM_OF_CONNECTION_TYPES) {
+    if (!had_connection_type[type]) {
+      had_connection_type[type] = true;
+      counter1.Add(type);
+    }
+  }
+  counter2.Add(type);
+}
+
+}  // namespace net