Less string copies of text in XML parsing.

Change-Id: I5bf80de3da7ae4bd91dd7675a9af16d377c014aa
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/366409
Reviewed-by: Florin Malita <fmalita@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
2 files changed