Reenable smoothness top_25 benchmarks on reference build.

BUG=547833
TBR=nednguyen@google.com
CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_10_10_perf_bisect;tryserver.chromium.perf:win_perf_bisect

Review URL: https://codereview.chromium.org/1499093005

Cr-Commit-Position: refs/heads/master@{#364269}
diff --git a/tools/perf/benchmarks/smoothness.py b/tools/perf/benchmarks/smoothness.py
index 93e7a10e..d0aa60a 100644
--- a/tools/perf/benchmarks/smoothness.py
+++ b/tools/perf/benchmarks/smoothness.py
@@ -36,7 +36,6 @@
     return True
 
 
-@benchmark.Disabled('reference') # crbug.com/547833
 class SmoothnessTop25(_Smoothness):
   """Measures rendering statistics while scrolling down the top 25 web pages.
 
@@ -158,7 +157,6 @@
 
 
 @benchmark.Enabled('android', 'mac')
-@benchmark.Disabled('reference') # crbug.com/547833
 class SmoothnessGpuRasterizationTop25(_Smoothness):
   """Measures rendering statistics for the top 25 with GPU rasterization.
   """