Remove yet-unused 64-bit atomic hooks.

src/ports/SkAtomics_sync.h

Index: src/ports/SkAtomics_sync.h
diff --git a/src/ports/SkAtomics_sync.h b/src/ports/SkAtomics_sync.h
index 8135ae2e2ae28714bc6d133fa25c2c318231a86b..ed9e3d1695a1221345a78616db07ec49e4f02620 100644
--- a/src/ports/SkAtomics_sync.h
+++ b/src/ports/SkAtomics_sync.h
@@ -24,18 +24,10 @@ static inline __attribute__((always_inline)) int32_t sk_atomic_add(int32_t* addr
     return __sync_fetch_and_add(addr, inc);
 }
 
-static inline __attribute__((always_inline)) int64_t sk_atomic_add(int64_t* addr, int64_t inc) {
-    return __sync_fetch_and_add(addr, inc);
-}
-
 static inline __attribute__((always_inline)) int32_t sk_atomic_dec(int32_t* addr) {
     return __sync_fetch_and_add(addr, -1);
 }
 
-static inline __attribute__((always_inline)) int64_t sk_atomic_dec(int64_t* addr) {
-    return __sync_fetch_and_add(addr, -1);
-}
-
 static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomic_dec() { }
 
 static inline __attribute__((always_inline)) bool sk_atomic_cas(int32_t* addr,
@@ -44,12 +36,6 @@ static inline __attribute__((always_inline)) bool sk_atomic_cas(int32_t* addr,
     return __sync_bool_compare_and_swap(addr, before, after);
 }
 
-static inline __attribute__((always_inline)) bool sk_atomic_cas(int64_t* addr,
-                                                                int64_t before,
-                                                                int64_t after) {
-    return __sync_bool_compare_and_swap(addr, before, after);
-}
-
 static inline __attribute__((always_inline)) void* sk_atomic_cas(void** addr,
                                                                  void* before,
                                                                  void* after) {