Telemetry: re-enable testRendering on CrOS

The fix (crrev.com/c/1097624) is already rolled (crrev.com/c/1098715)

Bug: 851523
Change-Id: I6a4f35eb1448b14c2a28864236bcde9785ee768a
Reviewed-on: https://chromium-review.googlesource.com/1098634Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566937}

tools/perf/measurements/rendering_unittest.py

@@ -2,7 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-from telemetry import decorators
 from telemetry.testing import options_for_unittests
 from telemetry.testing import page_test_test_case
 from telemetry.util import wpr_modes
@@ -28,7 +27,6 @@ class RenderingUnitTest(page_test_test_case.PageTestTestCase):
     self._options.browser_options.wpr_mode = wpr_modes.WPR_OFF
     self._options.pageset_repeat = 2
 
-  @decorators.Disabled('chromeos')  # crbug.com/851523
   def testRendering(self):
     ps = self.CreateStorySetFromFileInUnittestDataDir('scrollable_page.html')
     results = self.RunMeasurement(