Remove forceRenderTargetFlush (unused)

Remove forceRenderTargetFlush (unused)

Committed: http://code.google.com/p/skia/source/detail?r=13948

[bsalomon, 2014-03-25 17:40:50]

I think this is from the really old days when there was no GrContext and
SkGpuDevice talked directly to GrGpu

[robertphillips, 2014-03-25 17:44:34]

lgtm

[bsalomon, 2014-03-25 17:52:10]

The CQ bit was checked by bsalomon@google.com

[commit-bot: I haz the power, 2014-03-25 17:52:14]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/bsalomon@google.com/210253004/1

[commit-bot: I haz the power, 2014-03-25 18:00:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-25 18:00:05]

Retried try job too often on Build-Mac10.8-Clang-x86-Release-Trybot for step(s)
BuildBench, BuildEverything, BuildGm, BuildSkiaLib, BuildTests, BuildTools
http://skia-tree-status-staging.appspot.com/redirect/compile-buildbots/builds...

[bsalomon, 2014-03-25 20:54:12]

The CQ bit was checked by bsalomon@google.com

[commit-bot: I haz the power, 2014-03-25 20:54:15]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/bsalomon@google.com/210253004/110001

[commit-bot: I haz the power, 2014-03-25 22:07:27]

Change committed as 13948