Introduce IOSChromeMetricsServicesManagerClient

ios/chrome/browser/metrics/ios_chrome_metrics_service_accessor.h

 // Copyright 2015 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 IOS_CHROME_BROWSER_METRICS_IOS_CHROME_METRICS_SERVICE_ACCESSOR_H_
 #define IOS_CHROME_BROWSER_METRICS_IOS_CHROME_METRICS_SERVICE_ACCESSOR_H_
 
 #include <stdint.h>
 #include <string>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "components/metrics/metrics_service_accessor.h"
 
 namespace {
 class CrashesDOMHandler;
 }
 
 // This class limits and documents access to metrics service helper methods.
 // Since these methods are private, each user has to be explicitly declared
 // as a 'friend' below.
 class IOSChromeMetricsServiceAccessor : public metrics::MetricsServiceAccessor {
  private:
+  friend class IOSChromeMetricsServicesManagerClient;
+
   // TODO(blundell): Remove these //chrome classes as friends once they're no
   // longer used by the iOS port.
   friend class ::CrashesDOMHandler;
   friend class DataReductionProxyChromeSettings;
-  friend class MetricsServicesManager;
 
   FRIEND_TEST_ALL_PREFIXES(IOSChromeMetricsServiceAccessorTest,
                            MetricsReportingEnabled);
 
   // Returns true if metrics reporting is enabled.
   static bool IsMetricsAndCrashReportingEnabled();
 
   // Calls metrics::MetricsServiceAccessor::RegisterSyntheticFieldTrial() with
   // ApplicationContext's MetricsService. See that function's declaration for
   // details.
   static bool RegisterSyntheticFieldTrial(const std::string& trial_name,
                                           const std::string& group_name);
 
   // Calls
   // metrics::MetricsServiceAccessor::RegisterSyntheticFieldTrialWithNameHash()
   // with ApplicationContext's MetricsService. See that function's declaration
   // for details.
   static bool RegisterSyntheticFieldTrialWithNameHash(
       uint32_t trial_name_hash,
       const std::string& group_name);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IOSChromeMetricsServiceAccessor);
 };
 
 #endif  // IOS_CHROME_BROWSER_METRICS_IOS_CHROME_METRICS_SERVICE_ACCESSOR_H_