Disabled tab_switching.five_blank_pages on Mac until we can fix issues with histogram buckets

BUG=455349

Review URL: https://codereview.chromium.org/866913006

Cr-Commit-Position: refs/heads/master@{#314679}

tools/perf/benchmarks/tab_switching.py

@@ -44,6 +44,7 @@ class TabSwitchingTypical25(benchmark.Benchmark):
     return 'tab_switching.typical_25'
 
 
+@benchmark.Disabled('mac')  # http://crbug.com/455349
 @benchmark.Enabled('has tabs')
 class TabSwitchingFiveBlankTabs(benchmark.Benchmark):
   """This test records the MPArch.RWH_TabSwitchPaintDuration histogram.