Add runs/ms to perf dashboard unit info.

tools/perf/unit-info.json

 {
   "_description" : "This file contains info about our performance test units, used by the perf dashboard (http://chromeperf.appspot.com).",
 
   "%": {
     "improvement_direction": "down",
     "why": "Percent CPU usage"
   },
   "bytes": {
     "improvement_direction": "down"
   },
@@ skipping 63 matching lines @@
   "points": {
     "improvement_direction": "up",
     "why": "Synonym for score, used in ChromeOS touchpad tests"
   },
   "ports": {
     "improvement_direction": "down"
   },
   "relocs": {
     "improvement_direction": "down"
   },
+  "runs/ms": {

[tonyg, 2014/01/05 20:10:13]

This is fine, but I'd just like to check first whether it might make sense to
change the test to report runs/s instead of adding a new unit. If this number
goes fractional, it might start to interfere with our ability to catch
regressions (I think we assume no test needs more than 2 decimal places or
something).

+    "improvement_direction": "up"
+  },
   "runs/s": {
     "improvement_direction": "up"
   },
   "runs_per_second": {
     "improvement_direction": "up"
   },
   "score": {
     "improvement_direction": "up"
   },
   "score_(bigger_is_better)": {
     "improvement_direction": "up"
   },
   "score (bigger is better)": {
     "improvement_direction": "up"
   },
   "sec": {
     "improvement_direction": "down"
   },
   "seconds": {
     "improvement_direction": "down"
   },
   "us": {
     "improvement_direction": "down"
   }
 }