identify_transfer_fn: Return C string for PQ and HLG

Bug: skia:420956739
Change-Id: I191522b0822a53d8c49dd38ff72412145c5095c5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1028316
Reviewed-by: Brett Somocurcio <brettos@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Florin Malita <fmalita@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed