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

chrome/browser/safe_browsing/incident_reporting/preference_validation_delegate.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_SAFE_BROWSING_INCIDENT_REPORTING_PREFERENCE_VALIDATION_DELEGATE_H_
 #define CHROME_BROWSER_SAFE_BROWSING_INCIDENT_REPORTING_PREFERENCE_VALIDATION_DELEGATE_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
@@ skipping 14 matching lines @@
  public:
   PreferenceValidationDelegate(
       Profile* profile,
       std::unique_ptr<IncidentReceiver> incident_receiver);
   ~PreferenceValidationDelegate() override;
 
  private:
   // TrackedPreferenceValidationDelegate methods.
   void 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) override;
   void 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) override;
 
   Profile* profile_;
   std::unique_ptr<IncidentReceiver> incident_receiver_;
 
   DISALLOW_COPY_AND_ASSIGN(PreferenceValidationDelegate);
 };
 
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_INCIDENT_REPORTING_PREFERENCE_VALIDATION_DELEGATE_H_