Fix typo in FirstIndexOffset::Data

s/first_index_offset/first_instance_offset

Change-Id: I7f77490cf5e75002baaedcb319140dd329a087ac
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/42461
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
diff --git a/src/transform/first_index_offset.cc b/src/transform/first_index_offset.cc
index 29fe53f..f5f3026 100644
--- a/src/transform/first_index_offset.cc
+++ b/src/transform/first_index_offset.cc
@@ -86,11 +86,11 @@
 FirstIndexOffset::Data::Data(bool has_vtx_index,
                              bool has_inst_index,
                              uint32_t first_vtx_offset,
-                             uint32_t first_idx_offset)
+                             uint32_t first_inst_offset)
     : has_vertex_index(has_vtx_index),
       has_instance_index(has_inst_index),
       first_vertex_offset(first_vtx_offset),
-      first_index_offset(first_idx_offset) {}
+      first_instance_offset(first_inst_offset) {}
 
 FirstIndexOffset::Data::Data(const Data&) = default;