Disable moz, dhtml, and roborhornet_pro benchmarks on all OSes except Chrome OS

BUG=

Review URL: https://codereview.chromium.org/757233006

Cr-Commit-Position: refs/heads/master@{#307103}

tools/perf/benchmarks/page_cycler.py

@@ -32,6 +32,9 @@ class _PageCycler(benchmark.Benchmark):
         report_speed_index = options.report_speed_index)
 
 
+# This is an old page set, we intend to remove it after more modern benchmarks
+# work on CrOS.
+@benchmark.Enabled('chromeos')
 class PageCyclerDhtml(_PageCycler):
   page_set = page_sets.DhtmlPageSet
 
@@ -63,6 +66,9 @@ class PageCyclerMorejs(_PageCycler):
   page_set = page_sets.MorejsPageSet
 
 
+# This is an old page set, we intend to remove it after more modern benchmarks
+# work on CrOS.
+@benchmark.Enabled('chromeos')
 class PageCyclerMoz(_PageCycler):
   page_set = page_sets.MozPageSet
 

tools/perf/benchmarks/robohornet_pro.py

@@ -41,7 +41,10 @@ class _RobohornetProMeasurement(page_test.PageTest):
         scalar.ScalarValue(results.current_page, 'Total', 'ms', result))
 
 
-
+# We plan to remove this test because it doesn't give useful data, but
+# we need to wait until Chrome OS can implement support for more helpful
+# benchmarks.
+@benchmark.Enabled('chromeos')
 class RobohornetPro(benchmark.Benchmark):
   test = _RobohornetProMeasurement