Use uint32_t consistently for region op

An implicit conversion warning was being hidden by the use of -isystem
to include frameworks/native/include.

Bug: 31752268
Test: m -j
Change-Id: I008ef537a24311d58816fae12ef8c4aeaba07547
diff --git a/include/private/ui/RegionHelper.h b/include/private/ui/RegionHelper.h
index 6b9b460..83b05c7 100644
--- a/include/private/ui/RegionHelper.h
+++ b/include/private/ui/RegionHelper.h
@@ -66,7 +66,7 @@
         virtual ~region_rasterizer() { }
     };
     
-    inline region_operator(int op, const region& lhs, const region& rhs) 
+    inline region_operator(uint32_t op, const region& lhs, const region& rhs)
         : op_mask(op), spanner(lhs, rhs) 
     {
     }