SkOnce: 2 bytes -> 1 byte

include/private/SkOncePtr.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 SkOncePtr_DEFINED
 #define SkOncePtr_DEFINED
 
@@ skipping 48 matching lines @@
 template <typename T>
 class SkBaseOncePtr {
 public:
     template <typename F>
     T* get(const F& f) const {
         uintptr_t state = sk_atomic_load(&fState, sk_memory_order_acquire);
         if (state < 2) {
             if (state == 0) {
                 // It looks like no one has tried to create our pointer yet.
                 // We try to claim that task by atomically swapping our state from '0' to '1'.
+                // See SkOnce.h for why we use an acquire memory order here rather than relaxed.
                 if (sk_atomic_compare_exchange(
-                    &fState, &state, (uintptr_t)1, sk_memory_order_relaxed, sk_memory_order_relaxed)) {
+                    &fState, &state, (uintptr_t)1, sk_memory_order_acquire, sk_memory_order_acquire)) {
                     // We've claimed it.  Create our pointer and store it into fState.
                     state = (uintptr_t)f();
                     SkASSERT(state > 1);
                     sk_atomic_store(&fState, state, sk_memory_order_release);
                 } else {
                     // Someone else claimed it.
                     // We fall through to the spin loop just below to wait for them to finish.
                 }
             }
 
@@ skipping 16 matching lines @@
         // TODO: If state == 1 spin until it's not?
     }
 
     // fState == 0 --> we have not created our ptr yet
     // fState == 1 --> someone is in the middle of creating our ptr
     // else        --> (T*)fState is our ptr
     mutable uintptr_t fState;
 };
 
 #endif//SkOncePtr_DEFINED