Remove MetricsServiceObserver in favor of MetricsProvider.

chrome/browser/metrics/chrome_metrics_service_accessor.h

 // 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 CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_ACCESSOR_H_
 #define CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_ACCESSOR_H_
 
 #include <stdint.h>
 #include <string>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "chrome/browser/metrics/metrics_service_accessor.h"
 
-class ChromeBrowserMetricsServiceObserver;
 class Profile;
 
 namespace {
 class CrashesDOMHandler;
 class FlashDOMHandler;
 }
 
 namespace extensions {
 class ExtensionDownloader;
 class ManifestFetchData;
 class MetricsPrivateGetIsCrashReportingEnabledFunction;
 }
 
 namespace prerender {
 bool IsOmniboxEnabled(Profile* profile);
 }
 
 namespace system_logs {
 class ChromeInternalLogSource;
 }
 
 // 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 ChromeMetricsServiceAccessor : public MetricsServiceAccessor {
  private:
   friend bool prerender::IsOmniboxEnabled(Profile* profile);
-  friend class ::ChromeBrowserMetricsServiceObserver;
   friend class ChromeRenderMessageFilter;
   friend class ::CrashesDOMHandler;
   friend class DataReductionProxyChromeSettings;
   friend class extensions::ExtensionDownloader;
   friend class extensions::ManifestFetchData;
   friend class extensions::MetricsPrivateGetIsCrashReportingEnabledFunction;
   friend class ::FlashDOMHandler;
   friend class system_logs::ChromeInternalLogSource;
   friend class UmaSessionStats;
 
@@ skipping 26 matching lines @@
   // Same as RegisterSyntheticFieldTrial above, but takes a hash for the trial
   // name, rather than computing it from the string.
   static bool RegisterSyntheticFieldTrialWithNameHash(
       uint32_t trial_name_hash,
       const std::string& group_name);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ChromeMetricsServiceAccessor);
 };
 
 #endif  // CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_ACCESSOR_H_