Add StringReader to JsonArbitraryFieldNameBenchmark

Author: schlosna

src/main/java/com/fasterxml/jackson/perf/json/JsonArbitraryFieldNameBenchmark.java

@@ -26,6 +26,7 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.Reader;
+import java.io.StringReader;
 import java.nio.ByteBuffer;
 import java.nio.CharBuffer;
 import java.nio.charset.Charset;
@@ -93,6 +94,13 @@ JsonParser create(JsonFactory factory, Supplier<byte[]> jsonSupplier) throws IOE
                 return factory.createParser(charBufferReader);
             }
         },
+        STRING_READER() {
+            @Override
+            JsonParser create(JsonFactory factory, Supplier<byte[]> jsonSupplier) throws IOException {
+                StringReader reader = new StringReader(new String(jsonSupplier.get(), Charset.forName("UTF-8")));
+                return factory.createParser(reader);
+            }
+        },
         ;
 
         abstract JsonParser create(JsonFactory factory, Supplier<byte[]> jsonSupplier) throws IOException;