add flag to switch to SkTextEncoding

Bug: skia:2664
Change-Id: I3a565b6dd47e9e09deaadb7e0962d95420fe8935
Reviewed-on: https://chromium-review.googlesource.com/c/1358692
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613103}
1 file changed