Register metric Histogram names.

telemetry/telemetry/web_perf/timeline_based_measurement.py

Index: telemetry/telemetry/web_perf/timeline_based_measurement.py
diff --git a/telemetry/telemetry/web_perf/timeline_based_measurement.py b/telemetry/telemetry/web_perf/timeline_based_measurement.py
index 961ed9120e26de4bd13871c5ed8522fe83e4c61a..921162072e012e06e22baafe25064a2a83940fb8 100644
--- a/telemetry/telemetry/web_perf/timeline_based_measurement.py
+++ b/telemetry/telemetry/web_perf/timeline_based_measurement.py
@@ -284,6 +284,9 @@ class TimelineBasedMeasurement(story_test.StoryTest):
       chrome_config.category_filter.AddIncludedCategory('blink.console')
     platform.tracing_controller.StartTracing(self._tbm_options.config)
 
+  def GetTimelineBasedMetrics(self):
+    return self._tbm_options.GetTimelineBasedMetrics()
+
   def Measure(self, platform, results):
     """Collect all possible metrics and added them to results."""
     platform.tracing_controller.telemetry_info = results.telemetry_info
@@ -291,11 +294,13 @@ class TimelineBasedMeasurement(story_test.StoryTest):
     trace_value = trace.TraceValue(results.current_page, trace_result)
     results.AddValue(trace_value)
 
-    try:
-      if self._tbm_options.GetTimelineBasedMetrics():
-        assert not self._tbm_options.GetLegacyTimelineBasedMetrics(), (
-            'Specifying both TBMv1 and TBMv2 metrics is not allowed.')
-        self._ComputeTimelineBasedMetrics(results, trace_value)
+    if self.GetTimelineBasedMetrics():
+      self._ComputeTimelineBasedMetrics(results, trace_value)
+      # Legacy metrics can be computed, but only if explicitly specified.
+      if self._tbm_options.GetLegacyTimelineBasedMetrics():
+        # Since this imports the trace model in python, it will also clean up
+        # the trace handles for us.
+        self._ComputeLegacyTimelineBasedMetrics(results, trace_result)
       else:
         # Run all TBMv1 metrics if no other metric is specified
         # (legacy behavior)
@@ -315,7 +320,7 @@ class TimelineBasedMeasurement(story_test.StoryTest):
       platform.tracing_controller.StopTracing()
 
   def _ComputeTimelineBasedMetrics(self, results, trace_value):
-    metrics = self._tbm_options.GetTimelineBasedMetrics()
+    metrics = self.GetTimelineBasedMetrics()
     extra_import_options = {
       'trackDetailedModelStats': True
     }