mac: Expose keychain access frequency to Telemetry.

base/perf_util.h

Index: base/perf_util.h
diff --git a/base/perf_util.h b/base/perf_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..9797b1e1536e5addab228eda859c438e695b2264
--- /dev/null
+++ b/base/perf_util.h
@@ -0,0 +1,24 @@
+// 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.
+
+#ifndef BASE_PERF_UTIL_H_
+#define BASE_PERF_UTIL_H_
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+
+namespace base {
+
+// Adds an entry to a local histogram to indicate that the keychain was
+// accessed. This function should be called each time the keychain is accessed
+// so that the number of entries in the histogram corresponds to the number of
+// times that the keychain is accessed.
+//
+// This local histogram is used by telemetry to track the number of times the
+// keychain is accessed.
+BASE_EXPORT void IncrementKeychainAccessHistogram();
+
+}  // namespace base
+
+#endif  // BASE_PERF_UTIL_H_