Remove SkThread::setProcessorAffinity()

It's only used by a couple unit tests.  We have other ways of getting
the same quality testing of our ref-count code now (e.g. TSAN).

BUG=skia:
CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Release-CMake-Trybot,Build-Mac10.9-Clang-x86_64-Release-CMake-Trybot

Review URL: https://codereview.chromium.org/1408213005
11 files changed