Add responsiveness_metric for timeline_based_measurement

tools/telemetry/telemetry/web_perf/metrics/timeline_based_metric.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 
+class TimelineBasedMetricException(Exception):
+  """Exception that can be thrown from metrics that implements
+  TimelineBasedMetric to indicate a problem arised when computing the metric.
+  """
+
+
+def _TimeRangesHasOverlap(iterable_time_ranges):
+  """ Returns True if there is are overlapped ranges in time ranges.
+  iterable_time_ranges: an iterable of time ranges. Each time range is a
+  tuple (start time, end time).
+  """
+  # Sort the ranges by the start time
+  sorted_time_ranges = sorted(iterable_time_ranges)
+  last_range = sorted_time_ranges[0]
+  for current_range in sorted_time_ranges[1:]:
+    start_current_range = current_range[0]
+    end_last_range = last_range[1]
+    if start_current_range < end_last_range:
+      return True
+    last_range = current_range
+  return False
+
+
 class TimelineBasedMetric(object):
   def __init__(self):
     """Computes metrics from a telemetry.core.timeline Model and a range
 
     """
     super(TimelineBasedMetric, self).__init__()
 
   def AddResults(self, model, renderer_thread, interaction_records, results):
     """Computes and adds metrics for the interaction_records' time ranges.
 
     The override of this method should compute results on the data **only**
     within the interaction_records' start and end time ranges.
 
     model is an instance of telemetry.core.timeline.model.TimelineModel.
     interaction_records is a list of instances of TimelineInteractionRecord.
     results is an instance of page.PageTestResults.
 
     """
     raise NotImplementedError()
+
+  def VerifyNonOverlappedRecords(self, interaction_records):
+    if _TimeRangesHasOverlap(((r.start, r.end) for r in interaction_records)):
+      raise TimelineBasedMetricException(
+        'This metric does not support interaction records with overlapped time '
+        'range.')
+    if _TimeRangesHasOverlap(((r.thread_start, r.thread_end)
+                              for r in interaction_records)):
+      raise TimelineBasedMetricException(
+        'This metric does not support interaction records with overlapped '
+        'thread time range.')