Revert of Disable storage.indexeddb_endure_tracing.reference perf test...

Revert of Disable storage.indexeddb_endure_tracing.reference perf test (patchset #1 id:1 of https://codereview.chromium.org/1355143002/ )

Reason for revert:
Ref build rolled in December (https://code.google.com/p/chromium/issues/detail?id=458538), trying to re-enable.

Original issue's description:
> Disable storage.indexeddb_endure_tracing.reference perf test
>
> The perf test is failing on the reference build turning the waterfall
> red.
>
> BUG=534409
>
> Committed: https://crrev.com/0a30f13172c1f8be4f0f6e462419c9287de733ab
> Cr-Commit-Position: refs/heads/master@{#349986}

TBR=sullivan@chromium.org,pmeenan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=534409

Review URL: https://codereview.chromium.org/1640803004

Cr-Commit-Position: refs/heads/master@{#371929}

tools/perf/benchmarks/indexeddb_perf.py

@@ -25,7 +25,6 @@ import os
 from core import path_util
 from core import perf_benchmark
 
-from telemetry import benchmark
 from telemetry import page as page_module
 from telemetry import story
 from telemetry.page import page_test
@@ -117,7 +116,6 @@ class IndexedDbOriginalSectioned(perf_benchmark.PerfBenchmark):
     return 'storage.indexeddb_endure'
 
 
-@benchmark.Disabled('reference') # http://crbug.com/534409
 class IndexedDbTracing(perf_benchmark.PerfBenchmark):
   """IndexedDB Performance tests that use tracing."""
   page_set = page_sets.IndexedDBEndurePageSet