Switch base::Value typemapping to be by value instead of by unique_ptr.

services/preferences/public/cpp/tracked/mock_validation_delegate.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 "services/preferences/public/cpp/tracked/mock_validation_delegate.h"
 
 MockValidationDelegateRecord::MockValidationDelegateRecord() = default;
 
 MockValidationDelegateRecord::~MockValidationDelegateRecord() = default;
 
@@ skipping 42 matching lines @@
 }
 
 MockValidationDelegate::MockValidationDelegate(
     scoped_refptr<MockValidationDelegateRecord> record)
     : record_(std::move(record)) {}
 
 MockValidationDelegate::~MockValidationDelegate() = default;
 
 void MockValidationDelegate::OnAtomicPreferenceValidation(
     const std::string& pref_path,
-    std::unique_ptr<base::Value> value,
+    const base::Optional<base::Value>& value,
     prefs::mojom::TrackedPreferenceValidationDelegate::ValueState value_state,
     prefs::mojom::TrackedPreferenceValidationDelegate::ValueState
         external_validation_value_state,
     bool is_personal) {
   record_->RecordValidation(
       pref_path, value_state, external_validation_value_state, is_personal,
       prefs::mojom::TrackedPreferenceMetadata::PrefTrackingStrategy::ATOMIC);
 }
 
 void MockValidationDelegate::OnSplitPreferenceValidation(
     const std::string& pref_path,
     const std::vector<std::string>& invalid_keys,
     const std::vector<std::string>& external_validation_invalid_keys,
     prefs::mojom::TrackedPreferenceValidationDelegate::ValueState value_state,
     prefs::mojom::TrackedPreferenceValidationDelegate::ValueState
         external_validation_value_state,
     bool is_personal) {
   record_->RecordValidation(
       pref_path, value_state, external_validation_value_state, is_personal,
       prefs::mojom::TrackedPreferenceMetadata::PrefTrackingStrategy::SPLIT);
 }