Replace bytewise copy loop with memcpy.

Using memcpy gives the optimizer more latitude to do smart things.
SkStrAppendU64 already had memcpy here; I just copy-pasted the code
over from there.

Change-Id: Id63881122acf544cb4457e708438ffb14479abdc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/534938
Reviewed-by: Ben Wagner <bungeman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
1 file changed