[Perf] Disable scheduler.tough_scheduling_cases on reference build

TBR=aiolos@chromium.org
BUG=549428
CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_10_10_perf_bisect;tryserver.chromium.perf:win_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect

Review URL: https://codereview.chromium.org/1428883003

Cr-Commit-Position: refs/heads/master@{#357062}

tools/perf/benchmarks/scheduler.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 import benchmark
 
 from core import perf_benchmark
-
 from measurements import smoothness
+
 import page_sets
 
 
+@benchmark.Disabled('reference')  # crbug.com/549428
 class SchedulerToughSchedulingCases(perf_benchmark.PerfBenchmark):
   """Measures rendering statistics while interacting with pages that have
   challenging scheduling properties.