Disable smoothness.gpu_rasterization.top_25_smooth on Nexus 6

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..256fc76a36be13efa06c965bddedfe2fa76230f6 100644
--- a/tools/perf/benchmarks/smoothness.py
+++ b/tools/perf/benchmarks/smoothness.py
@@ -139,6 +139,11 @@ class SmoothnessToughAnimationCases(_Smoothness):
   def Name(cls):
     return 'smoothness.tough_animation_cases'
 
+  @classmethod
+  def ShouldDisable(cls, possible_browser):
+    # crbug.com/596035
+    return possible_browser.platform.GetDeviceTypeName() == 'Nexus 6'
+
 
 @benchmark.Enabled('android')
 class SmoothnessKeySilkCases(_Smoothness):