Implement sk_atomic_conditional_inc with sk_atomic_cas.

Now that we have sk_atomic_cas, we can replace all the platform-specific CAS loops with one.

BUG=skia:
R=bungeman@google.com, mtklein@google.com, reed@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/300553003

git-svn-id: http://skia.googlecode.com/svn/trunk@14892 2bbb7eff-a529-9590-31e7-b0007b416f81
5 files changed