Revert of Parallel cache - preliminary

include/ports/SkAtomics_sync.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkAtomics_sync_DEFINED
 #define SkAtomics_sync_DEFINED
 
@@ skipping 28 matching lines @@
     barrier(mo);
     *ptr = val;
 }
 
 template <typename T>
 T sk_atomic_fetch_add(T* ptr, T val, sk_memory_order) {
     return __sync_fetch_and_add(ptr, val);
 }
 
 template <typename T>
-T sk_atomic_fetch_sub(T* ptr, T val, sk_memory_order) {
-    return __sync_fetch_and_sub(ptr, val);
-}
-
-template <typename T>
 bool sk_atomic_compare_exchange(T* ptr, T* expected, T desired, sk_memory_order, sk_memory_order) {
     T prev = __sync_val_compare_and_swap(ptr, *expected, desired);
     if (prev == *expected) {
         return true;
     }
     *expected = prev;
     return false;
 }
 
 template <typename T>
 T sk_atomic_exchange(T* ptr, T val, sk_memory_order) {
     // There is no __sync exchange.  Emulate it with a CAS loop.
     T prev;
     do {
         prev = sk_atomic_load(ptr);
     } while(!sk_atomic_compare_exchange(ptr, &prev, val));
     return prev;
 }
 
 #endif//SkAtomics_sync_DEFINED