Implement sk_atomic_conditional_inc with sk_atomic_cas.

src/ports/SkAtomics_android.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkAtomics_android_DEFINED
 #define SkAtomics_android_DEFINED
 
@@ skipping 14 matching lines @@
     return android_atomic_dec(addr);
 }
 
 static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomic_dec() {
     //HACK: Android is actually using full memory barriers.
     //      Should this change, uncomment below.
     //int dummy;
     //android_atomic_acquire_store(0, &dummy);
 }
 
-static inline __attribute__((always_inline)) int32_t sk_atomic_conditional_inc(int32_t* addr) {
-    while (true) {
-        int32_t value = *addr;
-        if (value == 0) {
-            return 0;
-        }
-        if (0 == android_atomic_release_cas(value, value + 1, addr)) {
-            return value;
-        }
-    }
-}
-
 static inline __attribute__((always_inline)) bool sk_atomic_cas(int32_t* addr,
                                                                  int32_t before,
                                                                  int32_t after) {
     // android_atomic_release_cas returns 0 for success (if *addr == before and it wrote after).
     return android_atomic_release_cas(before, after, addr) == 0;
 }
 
 static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomic_conditional_inc() {
     //HACK: Android is actually using full memory barriers.
     //      Should this change, uncomment below.
     //int dummy;
     //android_atomic_acquire_store(0, &dummy);
 }
 
 #endif