[js-perf-test] Adding micro benchmarks for for-in and keys patterns.

test/js-perf-test/JSTests.json

 {
   "name": "JSTests",
   "run_count": 5,
   "run_count_android_arm": 3,
   "run_count_android_arm64": 3,
   "timeout": 120,
   "units": "score",
   "total": true,
   "resources": ["base.js"],
   "tests": [
@@ skipping 117 matching lines @@
     },
     {
       "name": "Exceptions",
       "path": ["Exceptions"],
       "main": "run.js",
       "resources": ["try-catch.js"],
       "results_regexp": "^%s\\-Exceptions\\(Score\\): (.+)$",
       "tests": [
         {"name": "Try-Catch"}
       ]
+    },
+    {
+      "name": "Keys",
+      "path": ["Keys"],
+      "main": "run.js",
+      "resources": ["keys.js"],
+      "results_regexp": "^%s\\-Keys\\(Score\\): (.+)$",
+      "tests": [
+        {"name": "Object.keys()"},
+        {"name": "for (in)"},
+        {"name": "for (in) hasOwnProperty()"},
+        {"name": "for Object.keys()"},
+        {"name": "Object.keys().forEach()"},
+        {"name": "for (i < array.length)"},
+        {"name": "for (i < length)"}
+      ]
     }
   ]
 }