Convert //printing to use std::unique_ptr

printing/printing_context.cc

Index: printing/printing_context.cc
diff --git a/printing/printing_context.cc b/printing/printing_context.cc
index 2e080397a691ff91be558a7219dafbe2b04b2cea..5187ceed373f1b2654d76de09912db8b2bd9735a 100644
--- a/printing/printing_context.cc
+++ b/printing/printing_context.cc
@@ -49,7 +49,8 @@ PrintingContext::Result PrintingContext::OnError() {
 }
 
 PrintingContext::Result PrintingContext::UsePdfSettings() {
-  scoped_ptr<base::DictionaryValue> pdf_settings(new base::DictionaryValue);
+  std::unique_ptr<base::DictionaryValue> pdf_settings(
+      new base::DictionaryValue);
   pdf_settings->SetBoolean(kSettingHeaderFooterEnabled, false);
   pdf_settings->SetBoolean(kSettingShouldPrintBackgrounds, false);
   pdf_settings->SetBoolean(kSettingShouldPrintSelectionOnly, false);