Refactor BenchmarkResult.Add to take enum for data_type

tools/perf/benchmarks/spaceport.py

Index: tools/perf/benchmarks/spaceport.py
===================================================================
--- tools/perf/benchmarks/spaceport.py	(revision 222891)
+++ tools/perf/benchmarks/spaceport.py	(working copy)
@@ -10,6 +10,7 @@
 from telemetry import test
 from telemetry.core import util
 from telemetry.page import page_measurement
+from telemetry.page import result_data_type
 from telemetry.page import page_set
 
 
@@ -49,7 +50,7 @@
     for key in result_dict:
       chart, trace = key.split('.', 1)
       results.Add(trace, 'objects (bigger is better)', float(result_dict[key]),
-                  chart_name=chart, data_type='unimportant')
+                  chart_name=chart, data_type=result_data_type.UNIMPORTANT)
     results.Add('Score', 'objects (bigger is better)',
                 [float(x) for x in result_dict.values()])