Delete base/prefs and update callers to use components.

ios/chrome/browser/metrics/mobile_session_shutdown_metrics_provider_unittest.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/mobile_session_shutdown_metrics_provider.h"
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/prefs/testing_pref_service.h"
 #include "base/test/histogram_tester.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/metrics/metrics_service.h"
 #include "components/metrics/metrics_state_manager.h"
 #include "components/metrics/test_metrics_service_client.h"
+#include "components/prefs/testing_pref_service.h"
 #include "testing/gtest/include/gtest/gtest-param-test.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
 
 bool IsMetricsReportingEnabled() {
   return false;
 }
 
 }  // namespace
@@ skipping 147 matching lines @@
   // Now call the method under test and verify exactly one sample is written to
   // the expected bucket.
   metrics_provider_->ProvideInitialStabilityMetrics(nullptr);
   histogram_tester.ExpectUniqueSample("Stability.MobileSessionShutdownType",
                                       expected_buckets[GetParam()], 1);
 }
 
 INSTANTIATE_TEST_CASE_P(/* No InstantiationName */,
                         MobileSessionShutdownMetricsProviderTest,
                         testing::Range(0, 32));