Implement sk_atomic_conditional_inc with sk_atomic_cas.

src/ports/SkAtomics_win.h

Index: src/ports/SkAtomics_win.h
diff --git a/src/ports/SkAtomics_win.h b/src/ports/SkAtomics_win.h
index f4d6da4e3e28bdd5ae6c140a0a35962747898d7f..7454d66055157c347c533eb0430f787d87e7352a 100644
--- a/src/ports/SkAtomics_win.h
+++ b/src/ports/SkAtomics_win.h
@@ -36,23 +36,6 @@ 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) {
-    long value = *addr;
-    while (true) {
-        if (value == 0) {
-            return 0;
-        }
-
-        long before = _InterlockedCompareExchange(reinterpret_cast<long*>(addr), value + 1, value);
-
-        if (before == value) {
-            return value;
-        } else {
-            value = before;
-        }
-    }
-}
-
 static inline bool sk_atomic_cas(int32_t* addr, int32_t before, int32_t after) {
     return _InterlockedCompareExchange(reinterpret_cast<long*>(addr), after, before) == before;
 }