Revert "Revert "Use std::vector::front()/back() when inserting color stops""

This reverts commit da62fd052135065340a54ea0f6fb03d0b319e0f0.

Bug: oss-fuzz:55906
Change-Id: I89a4527574036dc32ebcc92cddafadc7bed5bde4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/654337
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Dominik Röttsches <drott@google.com>
1 file changed