[Perf] Disable smoothness.tough_scrolling_cases on reference build.

TBR=aiolos@chromium.org
BUG=549429

Review URL: https://codereview.chromium.org/1414193007

Cr-Commit-Position: refs/heads/master@{#357080}

tools/perf/benchmarks/smoothness.py

@@ -356,6 +356,7 @@ class SmoothnessGpuRasterizationPolymer(_Smoothness):
     return 'smoothness.gpu_rasterization.polymer'
 
 
+@benchmark.Disabled('reference')  # crbug.com/549429
 class SmoothnessToughScrollingCases(_Smoothness):
   page_set = page_sets.ToughScrollingCasesPageSet