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

extensions/browser/sandboxed_unpacker.h

 // Copyright (c) 2012 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 EXTENSIONS_BROWSER_SANDBOXED_UNPACKER_H_
 #define EXTENSIONS_BROWSER_SANDBOXED_UNPACKER_H_
 
 #include <string>
 
 #include "base/files/file_path.h"
@@ skipping 188 matching lines @@
   // Utility process crashed or failed while trying to install.
   void UtilityProcessCrashed();
 
   // Unzips the extension into directory.
   void Unzip(const base::FilePath& crx_path);
   void UnzipDone(const base::FilePath& directory, bool success);
 
   // Unpacks the extension in directory and returns the manifest.
   void Unpack(const base::FilePath& directory);
   void UnpackDone(const base::string16& error,
-                  std::unique_ptr<base::DictionaryValue> manifest);
+                  const base::Optional<base::DictionaryValue>& manifest);
   void UnpackExtensionSucceeded(
       std::unique_ptr<base::DictionaryValue> manifest);
   void UnpackExtensionFailed(const base::string16& error);
 
   // Reports unpack success or failure, or unzip failure.
   void ReportSuccess(std::unique_ptr<base::DictionaryValue> original_manifest,
                      const SkBitmap& install_icon);
   void ReportFailure(FailureReason reason, const base::string16& error);
 
   // Overwrites original manifest with safe result from utility process.
@@ skipping 52 matching lines @@
   // Utility client used for sending tasks to the utility process.
   std::unique_ptr<content::UtilityProcessMojoClient<mojom::ExtensionUnpacker>>
       utility_process_mojo_client_;
 
   DISALLOW_COPY_AND_ASSIGN(SandboxedUnpacker);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_SANDBOXED_UNPACKER_H_