Clean up some unused atomic routines.

include/private/SkAtomics.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_DEFINED
 #define SkAtomics_DEFINED
 
@@ skipping 135 matching lines @@
     std::atomic<T>* ap = reinterpret_cast<std::atomic<T>*>(ptr);
     return std::atomic_exchange_explicit(ap, val, (std::memory_order)mo);
 }
 
 // ~~~~~~~~ Legacy APIs ~~~~~~~~~
 
 // From here down we have shims for our old atomics API, to be weaned off of.
 // We use the default sequentially-consistent memory order to make things simple
 // and to match the practical reality of our old _sync and _win implementations.
 
-inline int32_t sk_atomic_inc(int32_t* ptr)            { return sk_atomic_fetch_add(ptr, +1); }
-inline int32_t sk_atomic_dec(int32_t* ptr)            { return sk_atomic_fetch_add(ptr, -1); }
-inline int32_t sk_atomic_add(int32_t* ptr, int32_t v) { return sk_atomic_fetch_add(ptr,  v); }
-
-inline int64_t sk_atomic_inc(int64_t* ptr) { return sk_atomic_fetch_add<int64_t>(ptr, +1); }
+inline int32_t sk_atomic_inc(int32_t* ptr) { return sk_atomic_fetch_add(ptr, +1); }
+inline int32_t sk_atomic_dec(int32_t* ptr) { return sk_atomic_fetch_add(ptr, -1); }
 
 #endif//SkAtomics_DEFINED