Use OS_LINUX instead of USE_OZONE in ui/gfx/ when possible

ui/gfx/mojo/buffer_types_struct_traits.h

Index: ui/gfx/mojo/buffer_types_struct_traits.h
diff --git a/ui/gfx/mojo/buffer_types_struct_traits.h b/ui/gfx/mojo/buffer_types_struct_traits.h
index 17b73a71e70968c6c1c18ab368f9c155bab47185..246e7055ac68f323d80d37b337688d8b6cf9c6af 100644
--- a/ui/gfx/mojo/buffer_types_struct_traits.h
+++ b/ui/gfx/mojo/buffer_types_struct_traits.h
@@ -235,10 +235,10 @@ struct StructTraits<gfx::mojom::NativePixmapHandleDataView,
                               void* context);
 
   static bool IsNull(const gfx::NativePixmapHandle& handle) {
-#if defined(USE_OZONE)
+#if defined(OS_LINUX)
     return false;
 #else
-    // NativePixmapHandle are not used on non-ozone platforms.
+    // NativePixmapHandle are not used on non-linux platforms.
     return true;
 #endif
   }