mac: Expose keychain access frequency to Telemetry.

base/mac/keychain_metrics.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 "base/critical_closure.h"
+#include "base/mac/keychain_metrics.h"
 
-#import <UIKit/UIKit.h>
+#include "base/metrics/histogram.h"
 
 namespace base {
-namespace internal {
+namespace mac {
 
-bool IsMultiTaskingSupported() {
-  return [[UIDevice currentDevice] isMultitaskingSupported];
+void IncrementKeychainAccessHistogram() {
+  LOCAL_HISTOGRAM_BOOLEAN("OSX.Keychain.Access", true);
 }
 
-}  // namespace internal
+}  // namespace mac
 }  // namespace base