Implement sk_atomic_conditional_inc with sk_atomic_cas.

src/ports/SkAtomics_none.h

Index: src/ports/SkAtomics_none.h
diff --git a/src/ports/SkAtomics_none.h b/src/ports/SkAtomics_none.h
index d44791c32c162befc683d56b471f58a542b63d5e..73cbf0af2253498974dacaf9145a3cf3bb965121 100644
--- a/src/ports/SkAtomics_none.h
+++ b/src/ports/SkAtomics_none.h
@@ -32,12 +32,6 @@ static inline int32_t sk_atomic_dec(int32_t* addr) {
 
 static inline void sk_membar_acquire__after_atomic_dec() { }
 
-static inline int32_t sk_atomic_conditional_inc(int32_t* addr) {
-    int32_t value = *addr;
-    if (value != 0) ++*addr;
-    return value;
-}
-
 static inline bool sk_atomic_cas(int32_t* addr, int32_t before, int32_t after) {
     if (*addr != before) return false;
     *addr = after;