Revert of Disabled the v8.todomvc reference build due to missing clock sync...

Revert of Disabled the v8.todomvc reference build due to missing clock sync markers (patchset #2 id:20001 of https://codereview.chromium.org/2340033002/ )

Reason for revert:
Root issue should be fixed.

Original issue's description:
> Disabled the v8.todomvc reference build due to missing clock sync markers
>
> TBR=nednguyen@chromium.org
> BUG=646925
>
> Committed: https://crrev.com/2c1a2b054e002dd463cdf88df02b3e20d550d0dd
> Cr-Commit-Position: refs/heads/master@{#418632}

TBR=nednguyen@chromium.org,oysteine@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=646925

Review-Url: https://codereview.chromium.org/2347493004
Cr-Commit-Position: refs/heads/master@{#418844}

tools/perf/benchmarks/v8.py

@@ -115,8 +115,6 @@ class _InfiniteScrollBenchmark(perf_benchmark.PerfBenchmark):
     return True
 
 
-# Disabled on reference builds due to http://crbug.com/646925
-@benchmark.Disabled('reference')
 class V8TodoMVC(perf_benchmark.PerfBenchmark):
   """Measures V8 Execution metrics on the TodoMVC examples."""
   page_set = page_sets.TodoMVCPageSet