Fix MetricsServiceClients to use SyncDisableObservers state.

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm

 // 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.
 
 #include "ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h"
 
 #include <stdint.h>
 
 #include <utility>
 #include <vector>
@@ skipping 356 matching lines @@
 void IOSChromeMetricsServiceClient::OnSyncPrefsChanged(bool must_purge) {
   if (!ukm_service_)
     return;
   if (must_purge) {
     ukm_service_->Purge();
     ukm_service_->ResetClientId();
   }
   // Signal service manager to enable/disable UKM based on new state.
   UpdateRunningServices();
 }
+
+bool IOSChromeMetricsServiceClient::IsHistorySyncEnabledOnAllProfiles() {
+  return SyncDisableObserver::IsHistorySyncEnabledOnAllProfiles();
+}