[tools/perf] Reference legacy_page_test module instead of page_test

tools/perf/measurements/task_execution_time.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.
 
-from telemetry.page import page_test
+from telemetry.page import legacy_page_test
 from telemetry.timeline.model import TimelineModel
 from telemetry.timeline import tracing_config
 from telemetry.util import statistics
 from telemetry.value import scalar
 
 
-class TaskExecutionTime(page_test.PageTest):
+class TaskExecutionTime(legacy_page_test.LegacyPageTest):
 
   IDLE_SECTION_TRIGGER = 'SingleThreadIdleTaskRunner::RunTask'
   IDLE_SECTION = 'IDLE'
   NORMAL_SECTION = 'NORMAL'
 
   _TIME_OUT_IN_SECONDS = 60
   _NUMBER_OF_RESULTS_TO_DISPLAY = 10
   _BROWSER_THREADS = ['Chrome_ChildIOThread',
                       'Chrome_IOThread']
   _RENDERER_THREADS = ['Chrome_ChildIOThread',
@@ skipping 193 matching lines @@
   def AddTask(self, name, duration):
     if name in self.tasks:
       # section_tasks already contains an entry for this (e.g. from an earlier
       # slice), add the new duration so we can calculate a median value later.
       self.tasks[name].Update(duration)
     else:
       # This is a new task so create a new entry for it.
       self.tasks[name] = NameAndDurations(name, duration)
     # Accumulate total duration for all tasks in this section.
     self.total_duration += duration