Refactor BenchmarkResult.Add to take enum for data_type

tools/perf/measurements/dromaeo.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from telemetry.core import util
 from telemetry.page import page_measurement
+from telemetry.page import result_data_type
 
 class Dromaeo(page_measurement.PageMeasurement):
   def MeasurePage(self, page, tab, results):
     js_is_done = 'window.document.cookie.indexOf("__done=1") >= 0'
     def _IsDone():
       return bool(tab.EvaluateJavaScript(js_is_done))
     util.WaitFor(_IsDone, 600, poll_interval=5)
 
     js_get_results = 'JSON.stringify(window.automation.GetResults())'
     print js_get_results
     score = eval(tab.EvaluateJavaScript(js_get_results))
 
     def Escape(k):
       chars = [' ', '-', '/', '(', ')', '*']
       for c in chars:
         k = k.replace(c, '_')
       return k
 
     suffix = page.url[page.url.index('?') + 1 : page.url.index('&')]
     for k, v in score.iteritems():
-      data_type = 'unimportant'
+      data_type = result_data_type.UNIMPORTANT
       if k == suffix:
-        data_type = 'default'
+        data_type = result_data_type.DEFAULT
       results.Add(Escape(k), 'runs/s', v, data_type=data_type)