Disabled netsim page cycler on mac due to redness/flakiness

BUG=353260

Review URL: https://codereview.chromium.org/801503002

Cr-Commit-Position: refs/heads/master@{#307989}

tools/perf/benchmarks/page_cycler.py

@@ -73,7 +73,7 @@ class PageCyclerMoz(_PageCycler):
   page_set = page_sets.MozPageSet
 
 
-@benchmark.Disabled('linux', 'win')  # crbug.com/353260
+@benchmark.Disabled('linux', 'win', 'mac')  # crbug.com/353260
 class PageCyclerNetsimTop10(_PageCycler):
   """Measures load time of the top 10 sites under simulated cable network."""
   tag = 'netsim'