Add runs/ms to perf dashboard unit info.

Review URL: https://codereview.chromium.org/119473003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243404 0039d316-1c4b-4281-b951-d872f2087c98

tools/perf/unit-info.json

@@ -81,6 +81,9 @@
   "relocs": {
     "improvement_direction": "down"
   },
+  "runs/ms": {
+    "improvement_direction": "up"
+  },
   "runs/s": {
     "improvement_direction": "up"
   },