[telemetry] Add support for composable process dumps in memory-infra

tools/telemetry/telemetry/web_perf/metrics/memory_timeline_unittest.py

 # Copyright 2015 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.
 
 import collections
 import unittest
 
 from telemetry.internal.results import page_test_results
 from telemetry.page import page
 import mock
 from telemetry.timeline import memory_dump_event
 from telemetry.web_perf.metrics import memory_timeline
 from telemetry.web_perf import timeline_interaction_record
 
 
 def MockProcessDumpEvent(dump_id, name, start, memory_usage):
   process_dump = mock.Mock()
   process_dump.dump_id = dump_id
   process_dump.process_name = name
   process_dump.start = start
+  process_dump.end = start
   if memory_usage is None:
     memory_usage = {}
   elif not isinstance(memory_usage, dict):
     memory_usage = dict.fromkeys(memory_timeline.DEFAULT_METRICS, memory_usage)
   process_dump.has_mmaps = any(metric in memory_usage for metric
                                in memory_timeline.DEFAULT_METRICS)
   process_dump.GetMemoryUsage = mock.Mock(return_value=memory_usage)
   return process_dump
 
 
@@ skipping 106 matching lines @@
                     for metric, value in stats1.iteritems())
     expected.update(('%s_gpu_process' % metric, [value])
                     for metric, value in stats2.iteritems())
     expected.update(('%s_total' % metric, [total]) for metric in metrics)
 
     model = MockTimelineModel([
         MockProcessDumpEvent('dump1', 'browser', 2, stats1),
         MockProcessDumpEvent('dump1', 'GPU Process', 5, stats2)])
     interactions = [TestInteraction(1, 10)]
     self.assertEquals(expected, self.getResultsDict(model, interactions))