telemetry: re-enalbe repaint.gpu_rasterization.key_mobile_sites

The skia bug suspected to cause this has been fixed.

R=tonyg@chromium.org
BUG=399125

Review URL: https://codereview.chromium.org/491583003

Cr-Commit-Position: refs/heads/master@{#291145}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291145 0039d316-1c4b-4281-b951-d872f2087c98

tools/perf/benchmarks/repaint.py

@@ -16,7 +16,6 @@ class RepaintKeyMobileSites(benchmark.Benchmark):
   page_set = page_sets.KeyMobileSitesPageSet
 
 
-@benchmark.Disabled('android')  # crbug.com/399125
 class RepaintGpuRasterizationKeyMobileSites(benchmark.Benchmark):
   """Measures repaint performance on the key mobile sites with forced GPU
   rasterization.