[js-perf-tests] Add classes benchmarks from SixSpeed.

test/js-perf-test/SixSpeed.json

Index: test/js-perf-test/SixSpeed.json
diff --git a/test/js-perf-test/SixSpeed.json b/test/js-perf-test/SixSpeed.json
index 021b58a3eaf059fe9283ee5d8371a62d121ade33..15a2792c6a74a63d32b3346f171d08e260c62f39 100644
--- a/test/js-perf-test/SixSpeed.json
+++ b/test/js-perf-test/SixSpeed.json
@@ -28,6 +28,31 @@
       ]
     },
     {
+      "name": "Classes",
+      "path": ["SixSpeed"],
+      "results_regexp": "^%s\\(Score\\): (.+)$",
+      "tests": [
+        {
+          "name": "ES5",
+          "main": "run.js",
+          "resources": ["classes/es5.js"],
+          "test_flags": ["classes/es5"]
+        },
+        {
+          "name": "Babel",
+          "main": "run.js",
+          "resources": ["classes/babel.js"],
+          "test_flags": ["classes/babel"]
+        },
+        {
+          "name": "ES6",
+          "main": "run.js",
+          "resources": ["classes/es6.js"],
+          "test_flags": ["classes/es6"]
+        }
+      ]
+    },
+    {
       "name": "Computed property names in object literals",
       "path": ["SixSpeed"],
       "results_regexp": "^%s\\(Score\\): (.+)$",