Add struct traits for base::Value.

chrome/utility/profile_import_handler.cc

Index: chrome/utility/profile_import_handler.cc
diff --git a/chrome/utility/profile_import_handler.cc b/chrome/utility/profile_import_handler.cc
index 3ec913dca319ac607f6ee468f8eec7e8580adeb1..cac83003cb5d0ed7f379df3a9354a92199b97e99 100644
--- a/chrome/utility/profile_import_handler.cc
+++ b/chrome/utility/profile_import_handler.cc
@@ -33,7 +33,7 @@ void ProfileImportHandler::Create(
 void ProfileImportHandler::StartImport(
     const importer::SourceProfile& source_profile,
     uint16_t items,
-    const base::DictionaryValue& localized_strings,
+    std::unique_ptr<base::DictionaryValue> localized_strings,
     chrome::mojom::ProfileImportObserverPtr observer) {
   content::UtilityThread::Get()->EnsureBlinkInitialized();
   importer_ = importer::CreateImporterByType(source_profile.importer_type);
@@ -54,7 +54,7 @@ void ProfileImportHandler::StartImport(
     ImporterCleanup();
   }
   bridge_ = new ExternalProcessImporterBridge(
-      localized_strings,
+      *localized_strings,
       ThreadSafeProfileImportObserverPtr::Create(std::move(observer)));
   import_thread_->task_runner()->PostTask(
       FROM_HERE, base::Bind(&Importer::StartImport, importer_,