Telemetry: smoothness measurement throws MissingTimelineMarker.

tools/perf/measurements/smoothness.py

Index: tools/perf/measurements/smoothness.py
diff --git a/tools/perf/measurements/smoothness.py b/tools/perf/measurements/smoothness.py
index 47a7802b7af51579fa5a3a4b95b17da47f804739..1985d85a6db2633571c6a06b5252ccd0f4635e63 100644
--- a/tools/perf/measurements/smoothness.py
+++ b/tools/perf/measurements/smoothness.py
@@ -6,15 +6,23 @@ from metrics import smoothness
 from metrics.gpu_rendering_stats import GpuRenderingStats
 from telemetry.page import page_measurement
 
+
 class DidNotScrollException(page_measurement.MeasurementFailure):
   def __init__(self):
     super(DidNotScrollException, self).__init__('Page did not scroll')
 
+
 class MissingDisplayFrameRate(page_measurement.MeasurementFailure):
   def __init__(self, name):
     super(MissingDisplayFrameRate, self).__init__(
         'Missing display frame rate metrics: ' + name)
 
+
+class MissingTimelineMarker(page_measurement.MeasurementFailure):
+  def __init__(self):
+    super(MissingTimelineMarker, self).__init__('Timeline marker not found')
+
+
 class Smoothness(page_measurement.PageMeasurement):
   def __init__(self):
     super(Smoothness, self).__init__('smoothness')
@@ -57,7 +65,7 @@ class Smoothness(page_measurement.PageMeasurement):
                   smoothness.TIMELINE_MARKER)
               if s.parent_slice == None]
     if len(events) != 1:
-      raise LookupError, 'timeline marker not found'
+      raise MissingTimelineMarker()
     return events[0]
 
   def MeasurePage(self, page, tab, results):