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

tools/json_schema_compiler/test/arrays_unittest.cc

Index: tools/json_schema_compiler/test/arrays_unittest.cc
diff --git a/tools/json_schema_compiler/test/arrays_unittest.cc b/tools/json_schema_compiler/test/arrays_unittest.cc
index 29ca4a6d34877220357829f5a37338197e5eca68..939f685e1f6b0c16463d598088c0960e197cc5b7 100644
--- a/tools/json_schema_compiler/test/arrays_unittest.cc
+++ b/tools/json_schema_compiler/test/arrays_unittest.cc
@@ -41,8 +41,8 @@ static std::unique_ptr<base::DictionaryValue> CreateBasicArrayTypeDictionary() {
   return value;
 }
 
-static base::Value* CreateItemValue(int val) {
-  base::DictionaryValue* value(new base::DictionaryValue());
+std::unique_ptr<base::DictionaryValue> CreateItemValue(int val) {
+  std::unique_ptr<base::DictionaryValue> value(new base::DictionaryValue());
   value->Set("val", new base::FundamentalValue(val));
   return value;
 }