Refactor BenchmarkResult.Add to take enum for data_type

tools/perf/benchmarks/kraken.py

Index: tools/perf/benchmarks/kraken.py
===================================================================
--- tools/perf/benchmarks/kraken.py	(revision 222891)
+++ tools/perf/benchmarks/kraken.py	(working copy)
@@ -11,7 +11,11 @@
 from telemetry.page import page_measurement
 from telemetry.page import page_set
 
+# Get build scripts into our path.
+util.AddDirToPythonPath(util.GetChromiumSrcDir(), 'build', 'util', 'lib')
+from common import perf_result_data_type # pylint: disable=F0401
 
+
 def _Mean(l):
   return float(sum(l)) / len(l) if len(l) > 0 else 0.0
 
@@ -34,7 +38,8 @@
     for key in result_dict:
       if key == 'v':
         continue
-      results.Add(key, 'ms', result_dict[key], data_type='unimportant')
+      results.Add(key, 'ms', result_dict[key],
+                  perf_result_data_type.UNIMPORTANT)
       total += _Mean(result_dict[key])
     results.Add('Total', 'ms', total)