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/ccpr/GrCCAtlas.cpp b/src/gpu/ccpr/GrCCAtlas.cpp
index 6dc523d..a41eb38 100644
--- a/src/gpu/ccpr/GrCCAtlas.cpp
+++ b/src/gpu/ccpr/GrCCAtlas.cpp
@@ -16,6 +16,7 @@
 #include "GrTextureProxy.h"
 #include "SkMakeUnique.h"
 #include "SkMathPriv.h"
+#include <atomic>
 
 class GrCCAtlas::Node {
 public:
@@ -154,8 +155,8 @@
 }
 
 static uint32_t next_atlas_unique_id() {
-    static int32_t nextID;
-    return sk_atomic_inc(&nextID);
+    static std::atomic<uint32_t> nextID;
+    return nextID++;
 }
 
 const GrUniqueKey& GrCCAtlas::getOrAssignUniqueKey(GrOnFlushResourceProvider* onFlushRP) {