Disable smoothness.tough_animation_cases on low-end win bots

tools/perf/benchmarks/smoothness.py

Index: tools/perf/benchmarks/smoothness.py
diff --git a/tools/perf/benchmarks/smoothness.py b/tools/perf/benchmarks/smoothness.py
index 733a136129c52521e26b19d2ec427c1adbd7e993..1b113688dbf4977a80cc214abc5d59362039b676 100644
--- a/tools/perf/benchmarks/smoothness.py
+++ b/tools/perf/benchmarks/smoothness.py
@@ -1,6 +1,7 @@
 # Copyright 2013 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 multiprocessing
 
 from core import perf_benchmark
 
@@ -139,6 +140,12 @@ class SmoothnessToughAnimationCases(_Smoothness):
   def Name(cls):
     return 'smoothness.tough_animation_cases'
 
+  @classmethod
+  def ShouldDisable(cls, possible_browser):  # http://crbug.com/595737
+    # This test is flaky on low-end windows machine.
+    return (possible_browser.platform.GetOSName() == 'win' and
+            multiprocessing.cpu_count() <= 2)
+
 
 @benchmark.Enabled('android')
 class SmoothnessKeySilkCases(_Smoothness):