Don't use deprecated ListValue::Append(Value*) overload.

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

Index: chrome/browser/ui/webui/print_preview/print_preview_handler.cc
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
index 64a5c465c11abccacd991500239bb49ceb09afcc..28e220ab503a99ee2c4469da39b485b4f7a505b8 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
@@ -418,9 +418,8 @@ void EnumeratePrintersOnBlockingPoolThread(base::ListValue* printers) {
   print_backend->EnumeratePrinters(&printer_list);
 
   for (const printing::PrinterBasicInfo& printer : printer_list) {
-    base::DictionaryValue* printer_info = new base::DictionaryValue;
-    printers->Append(printer_info);
-
+    std::unique_ptr<base::DictionaryValue> printer_info(
+        new base::DictionaryValue);
     const auto printer_name_description = GetPrinterNameAndDescription(printer);
     const std::string& printer_name = printer_name_description.first;
     const std::string& printer_description = printer_name_description.second;
@@ -434,6 +433,8 @@ void EnumeratePrintersOnBlockingPoolThread(base::ListValue* printers) {
     for (const auto opt_it : printer.options)
       options->SetString(opt_it.first, opt_it.second);
 
+    printers->Append(std::move(printer_info));
+
     VLOG(1) << "Found printer " << printer_name << " with device name "
             << printer.printer_name;
   }