Simplify test file used by testBlinkPerfTracingMetricsForMeasureFrameTime & enable it on Android

tools/perf/benchmarks/blink_perf_unittest.py

 # Copyright 2017 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 os
 import unittest
 
-from telemetry import decorators
 from telemetry import story
 from telemetry.page import page as page_module
 from telemetry.testing import options_for_unittests
 from telemetry.testing import page_test_test_case
 from telemetry.timeline import async_slice
 from telemetry.timeline import model as model_module
 
 
 from benchmarks import blink_perf
 
@@ skipping 31 matching lines @@
     frame_view_layouts = results.FindAllPageSpecificValuesNamed(
         'FrameView::layout')
     self.assertEquals(len(frame_view_layouts), 1)
     self.assertGreater(frame_view_layouts[0].GetRepresentativeNumber, 0.1)
 
     update_layout_trees = results.FindAllPageSpecificValuesNamed(
         'UpdateLayoutTree')
     self.assertEquals(len(update_layout_trees), 1)
     self.assertGreater(update_layout_trees[0].GetRepresentativeNumber, 0.1)
 
-  @decorators.Disabled('android')  # crbug.com/715685
   def testBlinkPerfTracingMetricsForMeasureFrameTime(self):
     results = self.RunMeasurement(measurement=self._measurement,
         ps=self._CreateStorySetForTestFile(
             'color-changes-measure-frame-time.html'),
         options=self._options)
     self.assertFalse(results.failures)
     self.assertEquals(len(results.FindAllTraceValues()), 1)
 
     frame_view_prepaints = results.FindAllPageSpecificValuesNamed(
         'FrameView::prePaint')
@@ skipping 103 matching lines @@
     renderer_main.BeginSlice('blink', 'foo', 120)
     renderer_main.EndSlice(140)
 
     renderer_main.BeginSlice('blink', 'bar', 400)
     renderer_main.EndSlice(420)
 
     self.assertEquals(
         blink_perf._ComputeTraceEventsThreadTimeForBlinkPerf(
             renderer_main, ['foo', 'bar']),
         {'foo': [20], 'bar': [20]})