[pdf] Avoid entires in both unicode maps

In the current code if a font shapes "f" "f" "i" (U+66 U+66 U+69) to the
glyph <ffi> and also has a mapping from "ffi" (U+FB03) to the glyph <ffi>
then it is possible to get two entries for <ffi>. To avoid this, only
add an entry to the extended mapping if the base mapping does not have a
mapping for the glyph.

Bug: 40043392
Change-Id: I684e8fe82cc7ad9de55e084e3ef9e727f902c64e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/915600
Reviewed-by: Florin Malita <fmalita@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed