SkShaper per-line callback

Tweak SkShaper to call out for each line, instead of bundling everything
as a text blob.

Change-Id: Ic522f88afcf31cefd873dc8b5cde1ac2e107c64f
Reviewed-on: https://skia-review.googlesource.com/c/176592
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
8 files changed