remove sk_atomic_inc

Change-Id: I4960b1cd055daf44637e95825f82cb7fe2ce134a
Reviewed-on: https://skia-review.googlesource.com/c/174285
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/src/gpu/ops/GrOp.cpp b/src/gpu/ops/GrOp.cpp
index 3a36d73..b8a0031 100644
--- a/src/gpu/ops/GrOp.cpp
+++ b/src/gpu/ops/GrOp.cpp
@@ -7,9 +7,8 @@
 
 #include "GrOp.h"
 
-int32_t GrOp::gCurrOpClassID = GrOp::kIllegalOpID;
-
-int32_t GrOp::gCurrOpUniqueID = GrOp::kIllegalOpID;
+std::atomic<uint32_t> GrOp::gCurrOpClassID {GrOp::kIllegalOpID + 1};
+std::atomic<uint32_t> GrOp::gCurrOpUniqueID{GrOp::kIllegalOpID + 1};
 
 #ifdef SK_DEBUG
 void* GrOp::operator new(size_t size) {