Structs already handled this appropriately, but interface blocks did not
guard against naming their member variables built-in type names like
"float" or "bool".
Change-Id: I12ec054b3f158b83e35031449cf2a088ff8d0dc2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/489596
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
