mojo_benchmark: aggregate results over multiple runs.

mojo/devtools/common/devtoolslib/perf_dashboard.py

Index: mojo/devtools/common/devtoolslib/perf_dashboard.py
diff --git a/mojo/devtools/common/devtoolslib/perf_dashboard.py b/mojo/devtools/common/devtoolslib/perf_dashboard.py
index f203edf79bc5c6feb065428b300e80fcc55d3539..d5388c352355460b20ee238ffeb367f9ca2fef16 100644
--- a/mojo/devtools/common/devtoolslib/perf_dashboard.py
+++ b/mojo/devtools/common/devtoolslib/perf_dashboard.py
@@ -40,6 +40,15 @@ class ChartDataRecorder(object):
         'units': units,
         'value': value}
 
+  def record_vector(self, chart_name, value_name, units, values):
+    """Records a single measurement value of a list of scalars type."""
+    if chart_name not in self.charts:
+      self.charts[chart_name] = {}
+    self.charts[chart_name][value_name] = {
+        'type': 'list_of_scalar_values',
+        'units': units,
+        'values': values}
+
   def get_chart_data(self):
     """Returns the JSON string representing the recorded chart data, wrapping
     it with the required meta data."""