Revert of Re-enable key silk case benchmarks on Android

Revert of Re-enable key silk case benchmarks on Android (https://codereview.chromium.org/279853002/)

Reason for revert:
Still failing on N5. e.g. 

http://build.chromium.org/p/chromium.perf/builders/Android%20Nexus5%20Perf/builds/393/steps/smoothness.fast_path.key_silk_cases/logs/stdio

BUG=355952
Original issue's description:
> Re-enable key silk case benchmarks on Android
> 
> All the known issues with these telemetry benchmarks have been fixed.
> 
> BUG=355952
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=270830

TBR=ernstm@chromium.org,skyostil@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=355952
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=270973

[tonyg, 2014-05-16 09:27:16]

Created Revert of Re-enable key silk case benchmarks on Android

[commit-bot: I haz the power, 2014-05-16 09:27:44]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tonyg@chromium.org/292453005/1

[commit-bot: I haz the power, 2014-05-16 09:28:35]

Change committed as 270973