Add a concat method to SkTInternalLList

Bug: skia:
Change-Id: I3d62aff691f6cc08b7995bd72dbfd6289c803c6a
Reviewed-on: https://skia-review.googlesource.com/20380
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
2 files changed