Buffers with HB_LANGUAGE_INVALID race since it will force
hb_buffer_guess_segment_properties to call hb_language_get_default which
is not thread safe. The user is required to pass a language string to
the shaper, but it may be malformed and hb_language_from_string may
return HB_LANGUAGE_INVALID. Detect this and use "und" as the language,
since the language really isn't known (RFC5646 4.1 5).
Bug: skia:10323
Change-Id: Icf2389e606eb1b635d7535e57be10cca23bf9d33
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/294999
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
94aed0be1f