Revert of perf: Disable battor.tough_video_cases on Mac as it is failing...

Revert of perf: Disable battor.tough_video_cases on Mac as it is failing consistenly (patchset #1 id:1 of https://codereview.chromium.org/2380783003/ )

Reason for revert:
BattOr SD Card was replaced.

Original issue's description:
> perf: Disable battor.tough_video_cases on Mac as it is failing consistenly
>
> BUG=650411
> CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.perf:android_s5_perf_cq;master.tryserver.chromium.perf:linux_perf_cq;master.tryserver.chromium.perf:mac_retina_perf_cq;master.tryserver.chromium.perf:winx64_10_perf_cq
> TBR=alexclarke@chromium.org
> NOTRY=true
>
> Committed: https://crrev.com/842ccca9d542b2e7b98ed3b10e6d35061f682895
> Cr-Commit-Position: refs/heads/master@{#421891}

TBR=alexclarke@chromium.org,skyostil@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=650411

Review-Url: https://codereview.chromium.org/2393673002
Cr-Commit-Position: refs/heads/master@{#422984}

tools/perf/benchmarks/battor.py

@@ -47,10 +47,9 @@ class _BattOrBenchmark(perf_benchmark.PerfBenchmark):
 
 # android: See battor.android.tough_video_cases below
 # win8: crbug.com/531618
-# mac: crbug.com/650411
 # crbug.com/565180: Only include cases that report time_to_play
 # Taken directly from media benchmark.
-@benchmark.Disabled('android', 'win8', 'mac')
+@benchmark.Disabled('android', 'win8')
 class BattOrToughVideoCases(_BattOrBenchmark):
   """Obtains media metrics for key user scenarios."""
   page_set = page_sets.ToughVideoCasesPageSet