Convert //ash from scoped_ptr to std::unique_ptr

ash/display/json_converter.cc

Index: ash/display/json_converter.cc
diff --git a/ash/display/json_converter.cc b/ash/display/json_converter.cc
index 352a2ffae0b8633f4ef42b2132b0b0e82917a197..e10cd4749108be4c7dac7cb91bdb96a14ef5d2ec 100644
--- a/ash/display/json_converter.cc
+++ b/ash/display/json_converter.cc
@@ -178,9 +178,9 @@ bool DisplayLayoutToJson(const display::DisplayLayout& layout,
   dict_value->SetBoolean(kDefaultUnifiedKey, layout.default_unified);
   dict_value->SetString(kPrimaryIdKey, base::Int64ToString(layout.primary_id));
 
-  scoped_ptr<base::ListValue> placement_list(new base::ListValue);
+  std::unique_ptr<base::ListValue> placement_list(new base::ListValue);
   for (const auto& placement : layout.placement_list) {
-    scoped_ptr<base::DictionaryValue> placement_value(
+    std::unique_ptr<base::DictionaryValue> placement_value(
         new base::DictionaryValue);
     placement_value->SetString(
         kPositionKey,