Spin off just SkLazyFnPtr from 305513002.

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 45ba63f305c5193dee30eca074123840b0811936..b0d17527f07f0c50271c09d9b6699423b72dd3fa 100644
--- a/src/ports/SkAtomics_sync.h
+++ b/src/ports/SkAtomics_sync.h
@@ -32,6 +32,12 @@ 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)) void* sk_atomic_cas(void** addr,
+                                                                 void* before,
+                                                                 void* after) {
+    return __sync_val_compare_and_swap(addr, before, after);
+}
+
 static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomic_conditional_inc() { }
 
 #endif