Enable chromecast gpu perf

The new #ifndef account for what the chromecast sdk
cannot handle (e.g. posix).

Bug: skia:6581
Change-Id: I3d64d25980d80185f8b95c05badee5f665d97cd3
Reviewed-on: https://skia-review.googlesource.com/13811
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
12 files changed